BI102
BI102 Lab
Packet
2012-2013
Required for ALL sections of BI102
(Including On-line Classes)
Bring the ENTIRE manual to the first day of lab!
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BIOLOGY LAB SAFETY REGULATIONS &
STUDENT RESPONSIBILITIES
Read these carefully. You are responsible for them!
1. Science labs are inherently dangerous due to chemicals present. Eating and drinking are
prohibited in the labs.
2. In case of injury, get the instructor, send someone for the instructor, or call for help
immediately.
3. Know where the fire extinguisher is. In case of fire in the lab, use common sense and play it
safe. If it’s your clothes on fire, yell "FIRE" and roll on the floor or use a coat to smother
flames. Chemical fires are dangerous. Water will often only make the situation worse. If
you see abundant flames or smell smoke from and unknown source, you should call out
"FIRE" and calmly, but quickly, evacuate the building, insisting others leave as well.
4. If you spill chemicals on you or your clothes, rinse the area immediately with running water.
If you splash chemicals in your eyes, go immediately to the eye wash station, turn on cold
water, remove the red caps and lean down so that the water bubbles into your eyes. Keep
rinsing while holding your eyes open and send someone else to get the instructor!
5. Protect your eyes. Handle all chemical, including stains, below eye level. Wear protective
goggles or glasses whenever you work with chemicals or microbes.
6. Wash your hands with soap and water whenever leaving the lab for a break or at the end of
class.
7. Wash your work area and spray it down with the disinfectant provided before each lab
begins.
8. Closed-toed shoes must be won at all times in the lab. Long pants are preferred, even in
warm weather, to protect legs. Old clothes without baggy sleeves are recommended.
9. Keep the lab counter uncluttered. Stow extra books and coats on the back counter if
available.
10. If you have long hair, tie it back to keep it out of your eyes and the chemicals.
11. Clean-up is your responsibility. Wash down your work area to remove spilled chemicals at
the end of lab. Wash all glassware and dry it, including slides and cover slips. Sweep up
broken glass and deposit it in the special cardboard container provided (not in the trash
cans). Clean out the sink if you have used it.
12. Know what you are working with at all times and be prepared should something go wrong.
Read the lab in advance and precisely follow all instructions.
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Biotechnology Project Summary
Biotechnology is a new and rapidly growing field that uses the concepts of biology to solve the
problems of the modern world. The techniques used in this field save us time and money,
improve our health and, in some cases protect the planet. As we become more and more
reliant on the various forms of biotechnology, we become more and more aware of the ethical
and environmental implications of using these technologies. As a result, biotechnology is often
a source of controversy and many people express a desire to regulate or even prohibit these
techniques.
The goal of this project is to introduce you to several different types of biotechnology. The
project will involve researching both the technique itself and any controversy surrounding its
use. Based on what you learn during your research, you group will propose some level of
regulation for your technology and develop two political campaign ads. One ad will support the
regulation of the technology and the other ad will oppose regulation. In the end, you should be
able to provide an informed opinion about the use of biotechnology to solve every day
problems.
General Overview*:
Week
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Activity
 Distribute Biotech in the News Worksheet
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Due: Biotech in the News Worksheet
Class discussion of interesting biotech
Groups and Topics Assigned
Due: How Does Our Technology Work? Topic List
Due: How Does Our Technology Work? Research
Due: Biotechnology Controversies Topic List
Due: Statement of Legislation
Due: Biotechnology Controversies Research
Group Presentations
Assignments (may vary by instructor):
1. Biotech in the News Worksheet: Graded individually. A worksheet will be distributed during the
first lab of the term.
2. Individual Research Assignments (2): Each student will submit a unique assignment. The
assignments of members of the same group should not overlap.
3. Presentation: Each group will describe the technology they were assigned. At the end of their
presentation, the group will propose some form of regulation for their technology and present
two campaign ads; one for and one against this regulation.
4. Team evaluation: At the end of the term each student will anonymously evaluate the
participation of each team member.
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Reference Format for General Biology
This class includes a research project and with research comes references. To avoid charges of
plagiarism, it is essential that you learn the proper way to cite the source of information in the
text of your paper and list complete references at the end of your paper. Plagiarism will result
in a score of zero on your assignment. You may already be plagiarizing without knowing it! Get
informed! Visit this site for a simple explanation of what is and is not plagiarism:
http://www.plagiarism.org/plag_article_what_is_plagiarism.html
Using References in Science
For the most part, scientists do not quote directly from papers but summarize the facts or
conclusions of a paper in one or a few sentences that are referenced at the end of a sentence.
You must practice summarizing previously published material in your own words. Points will be
taken away from your grade for using quotations from rather than summarizing your
references. After summarizing the data, cite the publication to which you are referring.
In Text Citation format: …(Author, Year).

Scientific citations include the author and the year of publication but not the page
number.
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Citations are placed in parentheses at the end of a sentence before the period.
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If one citation covers several sentences, you either place the citation at the end of each
sentence or put the citation at the end of your summary (this is the best, most
appropriate way to do it).
Your Reference List
Any resources cited in your text must be listed in proper format in the References section of
your paper. Your reference list allows the reader to find more information on the topics you
cited in the text of your paper and provides verification for your discussion section. Most
scientific publications require a format based on, but not exactly the same as APA (American
Psychological Association) format. Examples of format required for this class are provided on
the next page.
Reference List Format:
 For the format of different types of references, use the guide on the back of this page.
 References should be alphabetized by author’s last name (notice that all formats list
author last name first.
 Only references actually cited in your paper should be included in the reference list.
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Required Reference Format for General Biology:
1. Journal articles (including those accessed digitally)
Author(s). (year) Title of article, Journal name vol: pages.
Freas KE, PR Kemp (1983) Some relationships between environmental
reliability and seed dormancy in desert annual plants, Journal of Ecology 71:
211-217.
2. Books
Authors(s) (year) Book title, Publisher, City, State, and country where
publisher is located.
Fenner, M (1985) Seed ecology, Chapman and Hall, New York, NY, USA.
3. Edited books
Author(s) (year) Chapter title. In Book Title (names of editor(s), eds.),
Publisher, City, State, and Country, pages
Kemp PR (1989) Seed banks and vegetation processes in deserts. In Ecology of
Soil and Seed Banks (MA Leck, VT Parker, RL Simpson, eds.), Academic Press,
New York, NY, USA. 257-282.
4. Websites
Author(s)* (year**) Title of Webpage. Retrieved on <date you visited that
website> from <complete website URL>.
Backyard Gardener (no date) Seed Germination Database. Retrieved on
February 8, 2011 from http://www.backyardgardener.com/tm.html.
*Find the author at the very bottom of the page. If no author listed, use the sponsor of the website
(check the URL for the name before .com/.org/.gov)
**Some webpages lack a date of publication. If this is the case, put “no date” in the parentheses. You
should ask yourself if this really is a reliable resource if it doesn’t give you a date!
Notice that Book and Journal titles are always italicized or underlined. Chapter
titles and article titles are in normal font and only the first letter of the first
word is capitalized.
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Date due:
Name:
Pre-lab 1: Cells and Microscopes
1. A. Differentiate between a dissecting microscope and a compound light microscope. (see
section 6.1 of your textbook).
B. Which type will we be using in today’s lab?
2. Explain how you would determine the total magnification of an image viewed with a
microscope?
3. Differentiate between a prokaryotic and a eukaryotic cell. Which type of cells are we
observing in today’s laboratory?
4. Complete the following table regarding the various membrane-bound organelles. You may
have to do some Internet investigation to fill in some of the spots!
Organelle Name
Plant, animal
or all
eukaryotic
cells?
Function
Central vacuole
Chloroplast
Golgi Body
Mitochondria
Nucleus
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Can you see it with a
compound microscope ?
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Name:
Lab 1: Microscopes and Cells
By the end of this lab you should be able to:
 Use a compound light microscope
 Calculate the magnification of an image
 Prepare a wet mount
 Describe the basic structure of a cell
 Identify organelles that are visible with a compound light microscope
Exercise 1. Introduction to Microscopes:Most cells are so small that you cannot
distinguish between them with only your eyes. The structures within a cell are even smaller. We
can explore cells and their internal structure with instruments known as microscopes.
Microscopes contain specially shaped pieces of glass (lenses) that alter the path of light as it
travels through a specimen to your eye. In this class, you will become familiar with two types of
microscopes.
A dissecting microscope provides three-dimensional images at lower
magnifications. A compound microscope provides two-dimensional details with a wide range of
magnifications.
Obtain a compound microscope from the cabinet. Always carry a microscope with two hands
(one on the base and one on arm). Obtain a diagram of a microscope. As your instructor
describes the parts of the microscope and their function, label the diagram and fill in the
following chart.
Table 1. Microscope Anatomy and Function
Microscope part
Function
Coarse Focus
Adjustment Knob
Diaphragm
Fine Focus
Adjustment Knob
Mechanical Stage
Adjustment Knobs
Objective
Ocular
Stage
As you work, label each of these parts in Figure 1 (next page).
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Figure 1. The Binocular Microscope: Label the parts indicated by arrows. Use
Table 1 as a guide to the appropriate names of the microscope parts.
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Microscopes are complex instruments that require special care. The following procedures will help you
comfortably use a microscope.
A. Sitting at your microscope: Microscopes are designed for people who are sitting down with the
microscope directly in front of them. Bending over to look in a microscope will hurt your back!
1. Place your microscope directly in front of you.
2. Adjust the height of your chair so that you can easily look into your microscope.
B. Getting started with a slide:
1. Plug your microscope in and turn it on
2. Lower the stage completely.
3. Click the low power objective into place.
4. Place the slide into the slide holder on the stage.
5. Use the coarse adjust knob, focus the image you see through the oculars/
6. Use the fine adjust knob to “fine tune” the focusing.
7. If necessary, go up in magnification by clicking the medium power objective into place.
8. Use the fine adjust knob to “fine tune” the focusing. Never use the coarse adjust knob at
medium or high power.
9. If necessary, go up in magnification by clicking the high power objective into place. Repeat
step 7.
C. Getting the best image (critical illumination): In order to get the best view of your specimen (this
means actually being able to see organelles within cells!), you will need to learn to set it up
appropriately.
1. Use the condenser adjustment knob to raise the condenser to the top (almost touching the
stage).
2. Lower the condenser slightly (about ¼ of a turn)
3. Adjust the iris diaphragm (the lever on the front of the condenser) until you see a
comfortable level of contrast when looking at a specimen. This level will probably need to
be readjusted at every magnification you use.
D. Putting away your microscope:
1. Click the lowest power objective lens (4X) in place and use the coarse focus adjustment
knob to raise the objective completely.
2. Turn off the light
3. Remove your slide and return it to the proper slide tray.
4. Unplug the microscope and loosely coil the microscope cord in your hand. Drape the coil
over the ocular lens(es).
5. Replace the dust cover.
6. Return the microscope to its cabinet such that the arm of the microscope is facing you.
Hints for looking at specimens:
1. If you lose your specimen, go back down to low power and start again. It won’t take too long
and it will save you a great deal of frustration.
2. To avoid losing your specimen, make sure that it is in the center of your field of view before
you go up in magnification.
3. If you can’t find your specimen, go to the edge of the slide and find the edge of the cover
slip. Get the edge of the cover slip into focus. Your specimen should be in the same focal
plane as the edge of the cover slip.
4. Do not use the coarse adjust knob at medium and high power. Not only do you risk damage
to your slide and your microscope, you are likely to go so far out of focus that you will lose
your specimen.
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Exercise 2. Your first slides:
1. Obtain a slide of the letter “e.”
a. Place the slide on to the stage so that it is right side up (so you would be able to read it).
b. Examine the slide with the lowest magnification on your microscope.
c. Sketch the letter “e” as you see it through your microscope in the margin of your
manual.

How does the orientation of the letter “e” as seen through the oculars of your
microscope differ from the actual orientation of the letter “e” on the stage of the
microscope?
2. Examine the letter “e” with at medium and high powers magnification.
 What happens to the amount of light in your field of view as you increase
magnification of your microscope?
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What happens to the amount of specimen you can see in one field of view as you
increase the magnification of your microscope?
3. Now, compute the total magnification available with each objective of your microscope.
a. Record your ocular magnification in appropriate sections of Table 2.
b. Record your objective magnifications in the appropriate sections of Table 2.
c. Multiply the magnification of the ocular by the magnification of the objective lens.
For example, a 10X eyepiece and a 10X lens would provide a total magnification of 100X (10x10). Fill in the
following chart (Table 2) for your microscope.
Table 2: Total Magnifications for Laboratory Microscopes
Ocular
Objective
Total Magnification
Magnification
Magnification
(Ocular X Objective)
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Exercise 3.Preparing a Wet Mount: The slides most students are familiar with are
prepared slides. To make a prepared slide a specimen is preserved, sliced and mounted
permanently on the slide for use by many students. Prepared slides usually incorporate stains
or dyes that highlight specific parts of the cell or tissue you are examining. In the laboratory you
can make your own slides of fresh material by preparing a wet mount. Dyes can also be used to
highlight cell structure in wet-mounted specimens.
General Procedure:
1. Obtain a clean slide and cover slip.
2. Place a drop of liquid (water or saline solution depending on the type of organism you are
examining) in the center of the slide.
3. Place the specimen in the drop of liquid. The specimen should be very small and as thin as
possible.
4. Hold the cover slip between your thumb and forefinger. Place one edge of the cover slip on
the slide near the left side of the liquid containing your specimen. The cover slip should be
at a 45° angle to the slide.
5. Slowly lower your cover slip onto the slide.
Prepare a wet mount of a portion of one leaf
of Elodea, a pond plant, for examination with
your microscope. The small green bodies in
the cytoplasm are chloroplasts. Their color is
due to the presence of chlorophyll. Move the
slide around and find a cell in which the
chloroplasts are moving.
This is called
cytoplasmic streaming.
Sketch a small portion of your field of view in
the space provided below.
a. Indicate the total magnification at
which you viewed the slide.
b. Label the chloroplast and central
vacuole.

Elodea
Total Magnification:
As you examine Elodea with your high power objective, carefully turn the fine focus
adjustment knob. What happens?
By turning the fine focus adjustment knob, you are looking at different layers of cells within the
Elodea leaf. Although we can place a three dimensional specimen under the compound
microscope, we can only obtain a two dimensional image of that specimen. The specimens in
prepared slides are sliced so thinly that focusing up and down is not necessary. In many living
specimens, focusing up and down allows us to examine different “slices” of a three dimensional
specimen. Estimate the number of layers of cells that form an Elodea leaf by focusing up and
down on your specimen:
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Exercise 4. Using Stains and Dyes to Examine Cell Structure:In this exercise, you will
not observe cells, You will learn how you can use a stain to locate a specific compound found in
some cells. Later in the lab, you will refer back to your observations to understand what you are
seeing within a cell.
Procedure:
1. Place three watch glasses on top of a piece of white paper.
2. Add a very small scoop (less than a pinch!) of sugar to one watch glass. Simple sugars like this
are a short-term form of energy storage in cells.
3. Add a very small scoop (less than a pinch!) of cornstarch to a second watch glass.Cornstarch
contains isolated leucoplasts or starch-storing structures from the cells of corn kernels. Starch is
an energy storage molecule produced by plants.
4. Add several drops of iodine solution (IKI) to the empty watch glass.

What color is the iodine solution?
5. Add several drops of iodine solution to the watch glass containing sugar.

What color is produced by mixing iodine and sugar?
6. Add several drops of iodine solution to the watch glass containing cornstarch.

What color is produced by mixing iodine and cornstarch?
7. Create a wet mount using only a few grains ofcornstarch and following the directions in the
previous exercise. Observe these leucoplasts with a microscope.

Are leucoplasts organelles? Explain your reasoning.
8. While your slide is still on the microscope, stain your sample with iodine solution using the
following method.
a. Place a drop of the stain on the slide next to the cover slip.
b. Twist the corner of a tissue into a point. Place the point at the edge of the other side of
the cover slip (opposite the drop of stain).
c. Capillary action will draw the stain under the cover slip.

What is the iodine actually staining in the cornstarch sample? The fluid or the
leucoplast?
You might want to sketch what you see in the margins for reference later in the lab.
Based on your observations, you should be able to draw a conclusion about how iodine solution
can be used in cells. Fill in the blank with your conclusion:
Conclusion:Iodine can be used to detect
(starch or sugar?) in cells.
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Exercise 5. Plant Cell Structure:Cells are the basic unit of life. Their importance, however,
was not understood until scientists were able to actually observe cells using the microscopic
techniques above. The rest of this lab is designed to encourage you to explore cell structure
with compound microscopes. Although we will be able to see some of the structural
components of a cell, many organelles are too small for us to see with these microscopes.
Plant cells contain several organelles that are not found in animal cells. All cells are surrounded
by a rigid cell wall and contain a central vacuole. Many plant cells contain chloroplasts, a green
organelle that is used for photosynthesis. Regions of the plant that do not perform
photosynthesis may contain other versions of chloroplasts that perform different functions in
the cell.
Plant cells also contain a variety of chemicals including the energy storage compounds we
discussed in exercise 4. Part of this exercise is to use the information you gained in exercise 4
to determine which energy storage compound (sugar or starch) is present in onion and potato
cells. Before you begin, complete the following hypotheses based on what you think the results
will be.


Onion epidermal cells contain the energy storage compound __________________.
Potato cells contain the energy storage compound_________________.
A. Onion Epidermal Cells: Go to the onion epidermal cell station in the lab. Carefully
follow the instructions at the station to prepare a wet mount of just the epidermis (an
outer skin-like tissue) of an onion.
Cells exhibit a great diversity in size, shape, and function, but each cell (whether plant or
animal) shows a basic similarity in intracellular organization. Perhaps the most obvious
structure in the cell is the nucleus. If you cannot see the nuclei, ask your instructor for help.
Notice that many of the nuclei appear to be pressed against the cell wall, the outer,
nonliving, cellulose envelope enclosing plant cells. The nucleus is restricted to this position
because of a large, fluid-filled central vacuole.
Onion epidermal cells
Draw several onion epidermal cells in the
space provided below.
a. Indicate the total magnification at which
you viewed the slide.
b. Label the nucleus and central vacuole of a
cell.

Usually, plant nuclei are shown pushed to
the side of the cell. How would you
account for the fact that some of the
nuclei in your onion cells appear to be
centrally located in the cells?
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Total Magnification:
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Stain your specimen with Iodine as described in Exercise 4.
 What happens? Describe your observations in detail!
 What type of energy storage compound (sugar or starch) is probably present in onion
epidermal cells?
B.Potato cells.Go to the potato station in the lab. Carefully follow the instructions at the
station to prepare a wet mount of a thin slice of potato cells.
Examine your slide of potato with your microscope. Many cells were cut open by the razor
blade releasing their contents.

What do you think the oval objects are that are scattered on the slide?
Stain the potato cells with iodine using the procedure outlined in Exercise 4.

What happens? Describe your observations in detail!
Draw a portion of your stained potato in the
space provided.
a. Indicate the total magnification at which
you viewed the slide.
b. Label the cell wall and any organelles you
see
Potato Cells
 Based on your results, what are the small
oval objects within potato cells?Hint: Check
out the “What to Expect” explanation at the end of the
instructions for this procedure.
Total Magnification:
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Exercise 6. Wet mounts of Single-celled Aquatic Organisms:The first organelles
evolved in single celled eukaryotes now categorized in to a broad group known as protists.
Protists exhibt a variety of organelles; both those that appear in multicellular organism and
several unique membrane-bound organelles that are seen in only one or a few species. To
examine a few of these unique organelles, let’s take a look at one of the larger protistan
species, Paramecium caudatum.
Procedure:
1. Obtain sample of Paramecium culture with a plastic pipette*. Look at the sample jar.
These organisms may be big enough to see with your eyes, but only as tiny moving
specks in the culture medium. Observation may show you the best place in the jar to
collect a sample. If you don’t see any specks, take your sample from near (but not at)
the bottom of the jar.
2. Place a drop of your sample on a clean slide.
3. Gently lower a coverslip over the drop as described earlier in the lab.
4. Place your slide on the microscope and focus on the edge of the coverslip. This will be
the easiest way to make sure you can find your specimen!
5. Use the scanning objective (4x) to find the organism.Paramecium tends to move
quickly. Have fun watching them swim for a minute!
6. Slow your Paramecium down. To get a closer look at the organelles in the Paramecium,
you will need to both increase your magnification and slow it down. Add a very small
drop of methylcellulose (Proto-slo) to the edge of both sides of your coverslip. This
substance will slowly diffuse under the coverslip and the Paramecium will slow. If all the
Paramecium are gone after adding methylcellulose, you added too much and will need
to make another slide.
7. Focus on a Paramecium with the highest power objective.Be sure to adjust your
contrast with the iris diaphragm so you can see its cilia and organelles! Use the
description below to identify the various organelles in this organism.
8. Sketch a Paramecium in the space provided on the next page. Make your drawing BIG!
Fill in the space! Label the visible structures highlighted in the description below.
* If live Paramecium are not available, your instructor will provide a prepared slide.
USE THIS DESCRIPTION TO IDENTIFY CELL STRUCTURES IN PARAMECIUM!
One of the first things you may see when you look at this organism is its hairy covering. Paramecium are
covered with thousands of tiny cilia. Cilia are extensions of the cytoskeleton surrounded by the plasma
membrane. The cilia beat back and forth much like the oars of a boat propelling the cell through its
aquatic environment.
Paramecium are often called “slipper” cells because of their shape. As the organism swims, it will roll a
bit and you will see a groove slanting downward toward the center of the cell. This structure is the
gullet, where food enters the cell. At the base of the gullet, food is captured in tiny vesicles that enter
the cell and fuse with lysosomes. Remember that lysosomes (which you cannot identify here) contain
digestive enzymes that will break down the food and release the nutrients to the cell. Together, the
lysosome and the food vesicle form a larger organelle known as a food vacuole. Food vacuoles may be
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visible in the cell you are examining. The color of this organelle depends on what food the Paramecium
is consuming.
Inside the organism you will notice several large organelles. The most obvious organelle is the large and
usually star-shaped contractile vacuole. The contractile vacuole plays an important role maintaining the
structure single-celled fresh water organisms. As we will learn next week, water tends to move into cells
by osmosis. If this process were to go unchecked, fresh water organisms like Paramecium would swell
and burst! The contractile vacuole found in many protists absorbs water and, when full, dumps it back
out into the environment. This is a continuous process and, if you watch long enough, you may be able
to see the contractile vacuole fill and dump in the organism you are observing.
The other organelle that will be visible in the Paramecium is the large macronucleus. Paramecium
actually contain two nuclei. The larger macronucleus is essential for producing the proteins responsible
for keeping the cell alive. The smaller micronucleus is essential for reproduction. The kidney-bean
shaped macronucleus is usually centrally located in the cell and has a dense or grainy appearance. If a
micronucleus is present is will be fairly close to the macronucleus in the indent of the kidney bean shape
of the macronucleus.
Paramecium caudatum
Total Magnification:
 Describe several ways that Protists like Paramecium differ from the plant cells we have
examined so far in this lab.
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Exercise 7: Animal Cell Structure: As you look at a representative animal cell, Compare its
structure to that of the plant cells you examined. What is similar? What is different?
A. Cheek cells: Go to the cheek cell station in the laboratory. Carefully follow the
instructions posted at the station to prepare a wet mount of your cheek cells.
 Note that instead of mounting your cheek cells in water, you are mounting them in a salt
solution. Why do you think that is?
Briefly examine your cheek cells with them microscope. Once you have a few cells in focus,
leave the slide in position on the microscope stage and stain the cells with methylene blue as
described in Exercise 4. Methylene blue is a stain that turns DNA blue.
Draw several cheek cells in the space
provided.
Human Cheek Cells
a. Indicate the total magnification
at which you viewed the slide.
b. Label the nucleus, plasma
membrane, and cytoplasm.
Did you observevery small blue dots on
the surface of your cheek cells. These
are bacteria, prokaryotic cells. Note
how much smaller they are than the
eukaryotic cells we are focusing on in
this lab!
Total Magnification:
B. Cells within organisms:Like plants, animals are multicellular and we usually cannot look
at isolated animal cells as we did with cheek cells. When arranged as a tissue, animal cells often
lack the characteristic “boxy” shape of the cells we saw in Elodea earlier in the lab and can be
harder to identify. The key to finding a single animal cell in a multicellular tissue is to look for
the nucleus. As we discovered in cheek cells, the centrally located nucleus of animal cells is
pretty large and usually stains darker than the rest of the cell. When you look at an animal
tissue specimen, look for these structures and remember that one nucleus = one cell.
Note: To understand this material, you must look at the slides in the order described!
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Procedure 1 (liver tissue, standard staining for contrast only):
1. Use your microscope to focus on a sample of liver tissue (slide = Liver section) at the
highest power magnification. Remember to center and focus the image with each of the
lower power objectives before increasing your magnification!
2. Identify a single cell on your slide.
3. Sketch several cells in the space provided on the next page. Label a single cell and its
nucleus.
4. Check with your instructor to make sure you have really found a cell before moving on
to the next step.
As we learned earlier in the lab, special stains can be used both to increase contrast in a
specimen, but also to highlight specific parts or compounds within a cell. To complete our
examination of animal cells, we will examine liver tissue, but this time, stained with a special
dye that highlights mitochondria, the organelles that produce power (ATP) in the cell.
Procedure2 (liver tissue, specially stained for mitochondria):
1. Use your microscope to focus on a sample of liver tissue with stained mitochondria
(slide = Mitochondria Amphiuma Liver) at the highest power magnification. Remember
to center and focus the image with each of the lower power objectives before increasing
your magnification!
2. Identify a single cell on your slide as described above. In addition to finding a nucleus,
each cell you see should contain many smaller, darkly stained dots. These are the
mitochondria.
3. Sketch several cells in the space provided. Label a single cell, its nucleus and a few
mitochondria.
Liver Cells
Liver Cells with stained Mitochondria
Total Mag:
Total Mag:
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Applying What You’ve Learned:

Why is it important to know the total magnification you are using when you are examining a
specimen with a microscope?

Complete the following table comparing the various organelles observed in this lab.
Plant, Protist,
Organelle
Function
Animal or all
eukaryotic cells?
Nucleus
Chloroplast
Mitochondria
Central vacuole
Food Vacuole
Contractile
Vacuole

Compare and contrast the arrangement of cells in multicellular plants (Elodea) and animals
(liver) based on what you observed in this lab.

Based on what you observed in this lab, how do animal cells differ from plant cells?

Describe several roles of stains and dyes in microscopy. Indicate specific exercises in this lab
that highlight these roles.
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Date due:
Name:
Pre-lab 2: Membranes
1. Differentiate between the processes of diffusion and osmosis.
2. Examine Figure 5.12 in your textbook and read the section on carbohydrates (section 5.7).
The glucose we are using in Exercise 2 in today’s lab is a monomer. The starch we are using
is a polymer.
A. Which of these molecules (starch or glucose) do you think is bigger?
B. Which of these molecules (starch or glucose) is more likely to travel through a
selectively permeable membrane?
3. Use the instructions for Exercise 3 (in this week’s lab) to sketch the 4 experimental set-ups
your group will create in class.
 Label the contents of each mock cell.
 Label the solution that will go on the outside of each mock cell.
The first one is done for you.
5%
sucrose
25% sucrose
Cell A
Cell C
A
Cell B
Cell D
4. When a hypertonic solution is separated from a hypotonic solution by a selectively
permeable membrane, which direction does water move?
Water moves from the
solution to the
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solution.
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Name:
Lab 2: Diffusion and Membrane Transport
Diffusion is a process in which molecules and particles move by random collisions and
eventually become randomly distributed throughout a solution. The result of this is the
apparent movement of those particles from high concentration toward low concentrations of
the substance that is diffusing. We say that the particles are diffusing along a concentration
gradient from high toward low concentration.
By the end of this lab, you should be able to:




Describe how diffusion takes place
Explain the similarities between diffusion and osmosis
Explain how size relates to the ability of materials to cross membranes
Describe the relationship between cell shape, size and function
Exercise 1. Cycles of Life Program 3(Permeable Packaging): Fill in the blanks as you
watch this short film.
1. Between the ..... inner cell and the ..... outside world stands the cell’s __________ .
2. The lipid molecules of the membrane naturally assemble in a __________ layerbecause
their tails__________ water as their heads __________ attract it.
3. Nature composes the (cell) membrane with a combination or __________ of different lipids,
carbohydrates and proteins. These molecules are not stationary, they constantly
move…__________ changing their position.
4. Diffusion is a fundamental physical process. Smaller molecules move directly through the
membrane as they travel from a __________ concentration to a __________concentration.
This process occurs naturally regardless of life.
5. Some proteins in a cell’s membranes act as__________ that allow specific large and/or
charged molecules to cross passively.
6. In passive diffusion passive transport the cell requires no__________.
7. When cells transport substances from a lower concentration to a higher one, they use
__________ proteins that act like a pump and need a boost from an __________ molecule.
8. In endocytosis, part of the surface membrane _________ surface material, forming a
(vesicle) which brings contents __________the cell.
9. In exocytosis, the sac forms internally, travels through the cytoplasm to the membrane and
fuses with the membrane releasing the contents __________ the cell.
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Exercise 2. Brownian Motion: All molecules are subject to naturally occurring movement.
Under the microscope, this movement will appear like a gentle vibration.
1. Put a drop of carmine dye suspension on a slide. Add a cover slip and place the slide on a
microscope. Let it sit for a couple of minutes to settle and for the cover slip to level out.
2. Observe the smallest particles on high power. If you see all the particles on your slide
moving across your field of view in the same direction, you should wait a bit longer. The
movement you are seeing is the flow of water across the slide. Ignore this movement!
When the slide has settled, you will be able to observe the movement of individual
particles.
What are the particles doing?
Look at a single particle. Does it always move in a single direction? Describe the path it
seems to follow.
This movement was first observed by Robert Brown who concluded that the particles must be
moving because water molecules were colliding with them (in spite of the fact that you cannot
see a water molecule).
Exercise 3: Diffusion: Membranes form the boundary of the cell and the boundary for most
cell organelles. They regulate the movement of materials between a cell and its environment
and between chambers within the cell itself. Do all molecules pass readily through a
membrane? What determines which particles will pass through a membrane and which won’t?
Procedure:
1. Fill a 150 mL beaker with water to within 2 cm of the top. Add enough IKI (iodine) solution to turn
the beaker contents a medium golden-brown. Put about 1 cm of this solution in a test tube for
use in the controls section (below).
2. Obtain a 15 cm piece of soaked dialysis tubing. Tie one end of the tube into a knot (the knot
should be as close to the end of the tubing as possible). Roll the tubing between your fingers to
open it up to a bag.
3. Use a dropper to pour starch solution into the bag to a depth of about 2 cm.
4. To the same bag add an equal amount of glucose solution.
5. Rinse off the outside of the bag to remove any spills.
6. Hang the dialysis tubing over the side of the beaker with the bag hanging in the iodine water.
Hang the other end outside of the beaker and use a rubber band to hold it in place.
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7. Set your beaker aside for about 30 minutes. While you wait, prepare the Control test tubes.
Controls: As you have probably learned in lecture, scientists use experiments, like the one
you’re doing now, to test their hypotheses. In an experiment, the conditions that a sample is
exposed to are changed slightly and observations are made as to how the sample responded to
that change. Experiments are both controlled and contain controls. Controlling an experiment
means that you maintain constant conditions (temperature, amount of solution, level of light,
etc) for all experimental treatments and controls. Generally, only one condition is changed at a
time (the experimental treatment). A control is a treatment in which the condition being tested
by the experiment is held constant. By including controls in their experiments, scientists can
compare the results of experimental treatments to their standard to determine if their
treatment actually causes a change.
Remember that the control is separate from the experimental sample. Conditions change in an
experimental treatment, but are maintained in a control. That being said, controls are often
classified as being positive or negative. A positive control is a one that is expected to show a
definite change. For example, the dye methylene blue stains DNA blue. A positive control for an
experiment testing for the presence of DNA might be a mixing purified DNA with Methylene
blue so that you can observe the exact color. Negative controls are expected to show little (or
slow) change. In the case of Methylene blue and DNA, we might combine Methylene blue with
a purified protein as a negative control to show that only DNA stains with this dye. Together,
the positive and negative controls can be compared to each of the experimental treatments to
determine if an experimental treatment had any affect.
Return to lab 1, exercise 4 to answer the following questions.
What was the positive control for the experiment performed in lab 1, exercise 4?
What was the negative control for the experiment performed in lab 1, exercise 4?
Prepare the controls for today’s experiment

Prepare 4 the four test tubes described in Table 1 by adding 1 cm of the required
solutions to each tube.

See the section on Benedict’s reagent below for the proper procedure.

Before continuing on to the “Interpreting Results section, complete the table by
explaining why each of these controls is important to this experiment.
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Table 1: Controls for Diffusion Experiment
Tube
#
Starting with…
Add equal
amount of…
1
IKI + water
(your beaker solution)
Starch stock
solution
2
Glucose stock solution
IKI
3
Glucose stock solution
Benedict’s
Reagent & Heat
4
Starch stock solution
Benedict’s
Reagent & Heat
Result of
Reaction
Purpose of this control
Benedict’s reagent Procedure:Benedict’s reagent is a chemical commonly used in medical
labs to indicate the presence of glucose in bodily fluids like urine. The presence of high levels of
glucose in urine is a symptom of diabetes. We will use Benedict’s reagent to test for the
diffusion of glucose. Use the following procedure:
1. Fill a 400 ml beaker with 2-3 cm of water. Place the beaker on a hot plate and bring the
water to boiling.
2. Mix an equal volume of the solution to be tested and Benedict’s reagent in a test tube
3. Place the test tube in the boiling water for 5 minutes. If glucose is present, you will see a
color change.
Analysis (Do not clean up yet! You have one more experiment to go!): After letting
the experiment sit for 30 minutes, examine the contents of the bag.
Can you tell if starch has moved out of the bag? Describe any observations that helped you
answer this question.
Can you tell if iodine has moved into the bag? Describe any observations that helped you
answer this question.
Explain how the control test tubes helped you understand these results.
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You also need to determine if glucose moved out of the bag.
Write out the step-by-step procedure your group will use to determine if glucose moved out of
the bag. Hint: look at the supplies provided in your kit for this lab!
Perform the procedure you described above.
Has glucose moved out of the bag? Describe any observations that helped you answer this
question.
In relative terms, a molecule of iodine is small, one of glucose is medium sized and a molecule of
starch is very big. What can we infer about the structure of the dialysis membrane we used in
this experiment based on the results of our experiment?
Exercise 4. Osmosis: Water molecules move along concentration gradients just like solute
molecules dissolved in the water, but they move in opposite directions. Water moves from
regions of low solute (“high water”) concentration to regions of high solute (“low water”)
concentration. The movement of water across membranes known as osmosis.
Procedure (Modified from Glick et al., The Process of Science: Seven Studies of Life):
1. Soak your dialysis tubing in distilled water for a minute or more. You will be using 4 pieces of tubing
to make 4 “mock” cells. Tie the tubing in a knot about 2 cm from one end. Open the other end of the
tubing by rubbing it together between your fingers.
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2. Write the letters A, B, C, or D in PENCIL on four tiny pieces of paper (they must fit into your dialysis
tubing).
3. Fill the bags about half full with the following solutions. After filling the bag, place the appropriate
label inside:
A. 5% sucrose
B. Distilled water
C. 10% sucrose
D. 25% sucrose
4. Force as much air out of the bag as possible by placing it between two fingers and moving your hand
away from the solution in the tubing. Tie the open end of the tube in a knot. The bag should be limp
after it is tied.
Based on what you’ve learned about osmosis, why would it be a bad idea to tie your bag just above
the solution or filled with air so that the bag is turgid? Hint: Read the introduction to exercise 4!
5. Squeeze your bag gently to check for leaks. If you find a leak, re-tie your bag.
6. Rinse your bag with tap water and blot it on a paper towel to remove excess water.
7. Place a weigh boat on a digital scale and press the zero or Tare button. This will set the weight of the
scale (and the weigh boat) to zero. Make sure the scale is set to measure grams (g).
8. Place your “cell” in the weigh boat and record its weight to the nearest 0.1 g in Table 2 (below) in
the column labeled “Weight at beginning of experiment.”
Table 2: Weight change over time during osmosis experiment
“Cell”
Predicted weight
change (+, –, 0)
Weight at beginning of
experiment (grams)
Weight at end of
experiment (grams)
Net change in weight
(+, –, 0)
A
B
C
D
9. When all the bags for your group are ready, place each bag into a 200 ml beaker of solution as
follows. Your beaker should contain about 80 ml of solution (just enough to cover your bag).
A. Put bag A into 25% sucrose
Put all of your bags into their
B. Put bag B into distilled water
C. Put bag C into distilled water
solutions at the same time!
D. Put bag D into distilled water
10. Once your experiment is running, make a prediction about how the weight of each bag will change
over the course of the experiment in the column labeled “Predicted weight change” in Table 2. You
can put a “+” for “weight will increase”, a “-" for “weight will decrease" and a “0” for "weight will
not change." You do not need to predict the amount of weight a bag might gain or lose.
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11. After 1 hour remove the bags from their solution and blot excess water away from the bag with a
paper towel. Weigh the bag to the nearest 0.1 g and record your results in Table 2 in the column
labeled “Weight at end of experiment”. Indicate weight gain for each bag with a “+”, weight loss
with a “-“and no change in weight with a “0” in the column labeled “Observed weight gain.
12. Place the 25% sucrose solution from Beaker A into the “Recycled 25% Sucrose” container. All other
solutions can go down the drain. Your mock cells can be placed in the garbage.
Analysis:
Is any of the samples in this experiment a negative control. Explain your reasoning.
Is any of the samples in this experiment a positive control. Explain your reasoning.
What caused the change in weight of your mock cells in this experiment? Is the change the
result of the movement of sugars or the movement of water? Explain your answer.
Explain the weight change in each bag based on the principles of osmosis. If the weight of a
bag did not change, explain why. In your explanation, use the terms hypertonic, hypotonic
and isotonic.
Bag A:
Bag B:
Bag C:
Bag D:
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Exercise 5. Osmosis in Elodea: The plant cell wall and the central vacuole play an
important roll in regulating osmosis in plants. Water that enters a plant cell through osmosis is
stored in the central vacuole. As the central vacuole swells with water, it pushes against the
cytoplasm and the cell wall (this is why all the chloroplasts are located at the outer edges of a
plant cell). Since the cell wall prevents plant cells from expanding, the influx of water creates
pressure and pressure inhibits osmosis. The pressure that builds up in plant cells is known as
turgor pressure. Turgor pressure is the force that keeps plants rigid. When a plant does not
have enough water, it cannot maintain pressure causing it to wilt.
We can actually see the response of plant cells to osmosis by subjecting the cells of Elodea to
different solutions. Your instructor has set up two microscopes with samples of Elodea. In one,
the Elodea is bathed in pure water. In the other, the Elodea is bathed in a highly concentrated
salt solution.
1. Which microscope (your instructor will have them labeled microscope A and B) contains
Elodea bathed in a high salt solution?
2. Explain your reasoning using the terminology appropriate to discussions of osmosis.
3. If you were to immerse an entire Elodea plant in salt water instead of just a few cells, how
would the plant change? Hint: consider the role of pressure in maintaining the structure of a plant
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Applying What You’ve Learned:

When evaluating the validity of an experiment, scientists always consider the control. The
results of an experiment that lacks control or has poorly designed controls are often
questioned or rejected. Why are controls so important?

Most non-scientists get their information about current research from “blurbs” on the
news. These blurbs seldom consider or discuss controls. Should you accept these news
stories as facts? Explain your reasoning.

How is Brownian motion (Exercise 2) important to the understanding of diffusion and
osmosis?

What factors govern the diffusion of a molecule across a membrane?

We learned that osmosis is the movement of water across a membrane. Besides a basic
need for water, why is the rate of osmosis important to a cell?
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Date due:
Name:
Pre-lab 3: Mitosis and the Cell Cycle
1.
Label the following stages of the cell
Interphase
cycle on the pie chart to the left:

G1

G2

S

Anaphase

Metaphase

Telophase

Prophase

Cytokinesis
Mitosis
2. Complete the following chart comparing the occurrences in the different stages of mitosis.
Some boxes have been completed for you.
Phase
Nucleus
Chromosomes
The spindle apparatus begins to
form. Spindle fibers attach to the
centromeres of duplicated
chromosomes
Prophase
Metaphase
––––
Anaphase
––––
Telophase
Spindle Fibers
Sister chromatids reach
opposite spindle poles
and begin to decondense
Turn over for one more question!
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3. Carefully read Exercise 4 in this week’s lab. Briefly describe how we can estimate the length
of time a growing onion root tip cell spends in each of the phases of the cell cycle.
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Name:
Lab 3: The Cell Cycle & Mitosis
By the end of this lab, you should be able to:
 Describe what happens during each phase of the cell cycle
 Use chromosome models or drawings to explain the process of mitosis to another
student
 Identify the stage of the cell cycle of a dividing cell
 Explain the differences between cell division in plants and animals
Exercise 1. Modeling the Cell Cycle with Play-Doh: The following exercises take you
through the steps of the cell cycle using chromosomes made of Play-Doh® as a model.
Chromosome Anatomy: Most cells in your body are diploid; they contain two copies of every
chromosome. One copy of each chromosome comes from your mother and the other copy
comes from your father. Chromosomes of the same type have the same shape and centromere
position (and have the same genes). Chromosomes of different types have different shapes and
centromere positions. Different types of chromosomes carry different genes.
You will model the cell cycle in a cell with a total of 4 chromosomes; two copies of each of two
types. To differentiate between the two types of chromosomes, you should make them
different lengths.
1. Obtain 2 jars of Play-Doh®.The jars should be different colors.
2. Divide the contents of each jar in half. Put one half of each color back in its jar for
now.
3. Use the Play-Doh® remaining on the counter to make one long snake and one short
snake of each color. You should now have 4 total snakes, two long (one of each
color) and two short (one of each color).
4. Begin by looking at one snake. This snake represents a chromosome, a piece of DNA
containing many genes.
5. Create four small balls of Play-Doh®(about the width of your snake) of a different
color (a third color, borrow a bit from a neighbor!) and place the ball in the center
of each chromosome. This structure is the centromere. The centromere is a
complex of proteins that binds microtubules and is important in the physical
separation of sister chromatids (read on to find out about these).
Are the chromosomes you built duplicated or unduplicated?
The cell cycle
1. Begin with a cell in G1 of interphase. Use a piece of chalk to draw a big circle on your
desktop (this represents a cell).Draw a circle inside this circle to represent the nucleus.
The circles should be big enough to fit your chromosomes inside!
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2. Place your unduplicated chromosomes in the center of your cell.Remember that in a
real cell, interphase chromosomes are not visible (even with the aid of a compound
microscope) to the human eye.
During this stage, the cell grows and performs its normal functions.
3. Move on to S phase and replicate your chromosomes by creating another, matching
Play-Doh® snake (chromosome)with centromere for each of the chromosomes already in
your cell (use the extra chunks of Play-Doh® that you set aside earlier). Attach the new
chromosomes to the chromosomes already in the cell. Remember that the centromeres
are what is holding them together!
How many pieces of DNA do you now have in your cell?
4. The structure you have created is still called a chromosome, but this duplicated
chromosome contains two identical sister chromatids. Each sister chromatid contains its
own centromere, but when they are stuck together, the centromeres overlap, appearing
as one.

How many duplicated chromosomes does your cell have after S phase?

Draw a diagram of a duplicated chromosome in the margins. Label the centromere
and the sister chromatids.
5. Not much happens to the chromosomes during G2. The cell grows and prepares for
mitosis by synthesizing important proteins and replicating many organelles.
6. Mitosis:
Mitosis is nuclear division, a process through which the nuclear material of the cell is
separated and distributed to newly forming cells. Mitosis is divided into five stages
based on the arrangement of the chromosomes in the cell.
Prophase:
Throughout interphase, the chromosomes were long and thread-like. During
prophase, the proteins associated with the DNA begin to aggregate (stick together)
making each chromosome shorter, fatter, and visible with a compound microscope.
The nuclear membrane breaks down and the spindle apparatus begins to play a
game of Tug-of-War to center the chromosomes. A microtubule from each
centrosome attaches to one of the centromeres in each duplicated chromosome
(one centromere of each duplicated chromosome is attached to each spindle pole).
Place your duplicated chromosomes randomly in the center of your workspace.
Metaphase:
As the game of Tug-of-War ends, the chromosomes are lined up in the middle of the
cell. Line up your chromosomes in the center of the cell.
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Anaphase:
During anaphase, attachments between the sister chromatids of duplicated
chromosomes are broken. Since the chromatids are no longer attached to each
other, they move up the microtubules of the spindle apparatus toward the spindle
poles. Separate the sister chromatids of each of your chromosomes and begin to
move them apart, toward their spindle poles.
Telophase:
This final phase of mitosis begins when the chromosomes reach the spindle poles.
The aggregation of chromosomes at each spindle pole becomes a nucleus. The
chromosomes then begin to decondense as the cytoplasm divides (see below) and
the resulting daughter cells enter G1 of interphase. Move your chromosomes to the
spindle poles.
7. Cytokinesis:
Cytokinesis, cytoplasmic division, is the last phase of the cell cycle and a topic of
another exercise in today’s laboratory. During this phase, the original mother cell is
divided into two independent daughter cells. This phase often occurs simultaneously
with telophase. The process of cytokinesis will be discussed later in this lab. Arrange
your chromosomes randomly in each of two nuclei to represent two different cells.

How many chromosomes are in each cell after mitosis and cytokinesis?
And that’s cell cycle! Try it one more time and then demonstrate the process to your instructor.
Get your instructors initials before moving on:
Exercise 2. Identifying cells in mitosis:In this exercise you will be using the microscope to
identify cells in various stages of cell division. We have two different types of prepared slides
for you to use, onion root tips and whitefish blastula, both of the slides contain a large number
of cells that have been preserved at various stages in the cell cycle.
Each student should work individually on this exercise! To begin, obtain a slide of Onion
(Allium) root tip. Since the tip of a root is a region of rapid plant growth, the cells are dividing
rapidly. This allows us to see cells of all the different stages of mitosis in one place. While each
of your slides should have cells that show all the stages of cell division any one cell is frozen in
the stage it is in forever – think of each of the cells as a snapshot of one particular time in the
cell cycle. Your job will be to identify cells in each of the stages of mitosis
Procedure:
1. Focus on a region where there are cells with visible chromosomes.
Remember to always start on the lowest power and only after you are in
focus on this power swing in the next most powerful objective. At the higher
powers only use the fine focus to sharpen your picture to avoid cracking the
slide.
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2. Once in focus with the 40X objective (this will be a total of 400X magnification!) you should be able to
identify the nucleus of the cell. This part of the cell is really what you need to pay the most attention
to; especially at first as you try to distinguish cells undergoing division from those still in interphase.
3. First find a cell with a nucleus that has a clear nucleus but no visible chromosomes (they would
appear as thick strands, almost wormlike) this is characteristic of a cell in interphase. Now sketch this
cell in the appropriate box below. Label any structures you can identify. Be sure to include total
magnification and any observations or comments you may have.
4. Now find a cell whose nucleus appears to be in prophase – if you can’t remember what to look for try
to remember the main occurrences you modeled in each of the phases in exercise one with the PlayDoh©. Now sketch this cell in the appropriate box below. Label any structures you can identify. Be
sure to include total magnification and any observations or comments you may have.
5. Continue on finding cells in metaphase, anaphase, and telophase –sketch each cell in the
appropriate box below. Label any structures you can identify. Be sure to include total magnification
and any observations or comments you may have.
Allium Root Tip: Interphase
Allium Root Tip: Prophase
Total Magnification:
Total Magnification
Allium Root Tip: Metaphase
Allium Root Tip: Anaphase
Total Magnification:
Total Magnification:
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Allium Root Tip: Telophase
Total Magnification:
Once you have observed all the stages of mitosis in an onion root tip cells, obtain a slide of a
whitefish blastula. A blastula is a very early embryo that consists of a ball of rapidly-dividing
cells. As a result, we can see cells in all the different stage of mitosis at once. Observing mitosis
in these cells may be more challenging as the cells are smaller and the contrast is not as great
as you saw with the onion root tip slide.
Procedure:
1. Obtain a slide of White Fish Blastula and set it up under low power on your
microscope. You will see a section of this ball of cells.
2. Center one slice in your field of view and use the proper procedure (outlined in lab 1) to
increase your total magnification to 450X.
3. Adjust the contrast of your microscope with the iris diaphragm.
4. Use the procedure outlined for the onion root slide to identify cells in each stage of
mitosis. Sketch a representative cell in the space provided below. Don’t forget to label
your drawings!
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Exercise 3. Comparing the cell cycle in plant and animal cells:Using the microscope,
two distinctions can be made between the cells cycles of plants and animals. The first involves
the presence or absence of centrioles and the second involves the process of furrowing. Use
your microscope to find examples of cytokinesis in plants and animals. In many cases,
cytokinesis and telophase occur simultaneously. To find a root tip cell undergoing cell plate
formation, look for a cell with two nuclei separated by a line that does not reach all the way
across the cell (the cell plate). To find a whitefish blastula cell (animal) undergoing cell plate
formation, look for a cell with an hourglass shape (like a figure 8). Now sketch an example of
each type of cytokinesis in the appropriate box below. You may have already drawn an
example of Allium in cytokinesis since telophase and cytokinesis often occur simultaneously.
Label any structures you can identify. Be sure to include total magnification and any
observations or comments you may have.
Allium Root Tip: Cytokinesis
Whitefish Blastula: Cytokinesis
Total Magnification:
Total Magnification:

Which type of organism (plant or animal) contains centrioles?Hint:
information from a textbook rather than your microscope!
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Exercise 4. Estimating the time spent in the phases of mitosis: Once you have
learned to distinguish the different stages of the cell cycle with your microscope, you can
perform a fun experiment to determine how long a cell spends in each stage of the cycle For
this exercise you will be looking at a large number of cells and deciding which phase each cell is
in. We can then use this information to decide how long each of these phases lasts.
Procedures:
1. For this exercise it will help to work in teams of two. Focus on the region of the root tip
containing dividing cells. One student should look in the microscope while the other acts
as a recorder.
2. The student looking in the microscope should identify the phase of cell division of 25
random cells within the field of view without counting any cell twice. Say the name of
the stage aloud so that the recorder can mark it down in Table 1 (next page).
3. After identifying 25 cells trade, jobs with your lab partner. Your lab partner should
identify the stages of 25 cells in a different field of view while you record the stages.
4. Record your group’s data on the class data table provided by your instructor. Wait until
all groups have posted their data before proceeding to the next step.
5. Calculate the percentage of time spent in each phase by counting the total number of
cells in each phase and dividing by the total number of cells you counted. Record the
percentage in the appropriate row of Table 2.
6. In an onion root tip the entire cell cycle take about 16 hours. To determine the time
spent in each phase of the cell cycle multiply the percentage of cells in each phase by
the total time of the cell cycle (16 hours). Record your answer in Table 2.
Table 1: Number of Cells in Each Stage of Mitosis
Your group
Class
Stage
Student 1 Student 2
Total
Total
Interphase
Prophase
Metaphase
Anaphase
Telophase
Total Cells
counted:
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Table 2. Estimate of time spent in each phase of cell cycle.
Phase 
Interphase
Prophase
Metaphase
Anaphase
Telophase
Total
% of cells in
each phase
100%
Time
estimate
16 hours

Why do we add all of the class data together before doing out calculations? Do you trust the count
that other students made? Why or why not?

Based on your calculations, what stage of the cell cycle is the longest? Provide a hypothesis as to
why this is the case?

Based on your calculations, what stage of mitosis is the longest? Provide a hypothesis as to why
this is the case?
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Applying What You’ve Learned:

Differentiate between an unduplicated chromosome and a duplicated chromosome (you
may want to include a sketch!).

During what stage(s) of the cell cycle and/or mitosis would you find the chromosomes in a
duplicated state?

What happens to the number of chromosomes in a cell during mitosis? For example, if a cell
enters mitosis with 8 chromosomes, how many chromosomes are found in each daughter
cell produced by mitosis?

A cell has two chromosomes. Sketch the chromosomes of that cell in each stage of mitosis.

Explain the difference in the cytokinesis between plant and animal cells.

For any given species, the length of mitosis is the same for all of its cell types, but the cell cycles of
different cell types vary greatly. How would the results of the experiment performed above be
affected if the cell cycle of the cells you observed was actually much longer than 16 hours (that is,
the cells were not actively dividing)?
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Date due:
Name:
Pre-lab 4: DNA Structure and Function
1. Define the following terms in your own words (remember that copying definitions from
published material, the internet or from another student is plagiarism).
DNA:
Nucleotide:
Mutation:
2. Use your lecture notes and textbook to draw a basic model of a nucleotide (don’t worry
about including all the chemical symbols). Label the three major parts of your model (sugar,
phosphate group and the base).
3. If the basic structure of all nucleotides is the same, where does the variability that gives us
each a unique genetic fingerprint come from?
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Date Due:
Name:
Lab 4: DNA Structure and Function
By the end of this lab, you should be able to:
 Draw a model of a single nucleotide
 Describe the structure of a DNA molecule
 Explain how DNA structure facilitates DNA replication
Exercise 1.The Genetic Code Puzzle (Part 1): In this exercise, we will examine DNA
structure and the process of DNA replication in detail. We will use a DNA puzzle kit with
cardboard pieces to model the structure and replication of DNA. In order to understand the
events in DNA replication it is important to work both with the correct pieces and assemble
them in the order described. Resist the temptation to skip steps.
Your team will need the following color-coded pieces:
24 Deoxyribose units (dark pink)
24 Phosphate units (yellow)
4 Adenine (A) units (light green)
4 Thymine (T) units (light blue)
8 Cytosine (C) units (dark green)
8 Guanine (G) units (dark blue)
CH2
5’
O
4’ C
C
1’
Deoxyribose
C
Ignore the large paper sheet and any other parts of the puzzle for now. 3’
C
2’
I.The DNA Nucleotides
A.ExamineDeoxyribose: Take a closer look at one of the deoxyribose units from the puzzle.
Deoxyribose is a five-sided ring sugar. The three knobs on the cardboard piece represent
sites where covalent chemical bonds can form between the sugar and bases or phosphates.
The molecule consists of a pentagon of four carbon atoms and one oxygen atom. Individual
carbon atoms are not shown on the puzzle piece, but are understood to be at the corners of
the pentagon (see drawing of deoxyribose above). To the left (counterclockwise) of the
oxygen atom in the ring, a methyl group (CH2) is bonded to the carbon in the ring. The ring
carbon attached to the methyl group is not shown on the puzzle piece. Chemists number the
carbons in a clockwise direction starting with the carbon to the right of the oxygen and
ending at the carbon in the methyl group (see drawing of deoxyribose above).
B. Build a nucleotide:
1. Attach a yellow phosphate to the methyl group on the deoxyribose.
2. Attach an adenine base (light green) to the free bond to the right of the oxygen.
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You have now built a representation of an adenine nucleotide from its three component parts.
Every nucleotide has these three parts: a sugar, a phosphate and a base. Before a cell can build
DNA, it must first assemble all of the 3-part nucleotides.
3. Use the remaining puzzle pieces to build 23 more nucleotides. Each member of your
group should assemble at least one nucleotide.
4. Set aside half OF EACH TYPE OF NUCLEOTIDE FOR USE LATER.

What is type of organic compound is deoxyribose?

In a DNA molecule, what molecule is attached to the 5'-Carbon on the deoxyribose?

In a DNA molecule, what molecule is attached to the 1'-Carbon on the deoxyribose?

Once a base has been attached to a sugar phosphate, what do we call the 3-part
molecule that results?

What are the 4 different bases that form nucleotides?
II. Base Pairing:
Certain bases are said to be complementary to each other. The exposed end of the base in a
nucleotide has a distinctive shape. The exposed edges of complementary bases will “fit
together.” The bases in your puzzle also have dotted lines extending off of the piece on the side
opposite the sugar attachment. These represent potential hydrogen bonding sites that can pair
up with a complementary base on the other side of the molecule.
1. Find the base that is complementary to adenine by trying to join one adenine nucleotide
with each of the other types of nucleotides you built.
2. Find the base that is complementary to guanine by trying to join one guanine nucleotide
with each of the other types of nucleotides you built.
 Adenine pairs only with _____________. Guanine pairs only with ____________.
 Does any of the bases pair with themselves?
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III. Building a strand of nucleotides:
The backbone of a side of the DNA molecule is constructed by covalently bonding nucleotides
to one another through the phosphate of one and the sugar of the next. Covalent bonds
between atoms are strong and difficult to break. When you covalently bond nucleotides
together, you end up with one side of a DNA molecule.
1. Select an adenine nucleotide and a guanine nucleotide.
2. Attach the phosphate of the guanine nucleotide to the sugar of the adenine
nucleotide.
3. Attach a thymine nucleotide to the sugar of the guanine nucleotide
You should now have a chain of 3 nucleotides! Let’s add a few more nucleotides!
4. Attach a cytosine to the thymine at the end of your chain of three nucleotides.
5. Attach a guanine to the cytosine
6. Attach a cytosine to the guanine.
The exposed phosphate end of the chain is called the 5' (5-prime) end because the #5 carbon of
the sugar is closest to this end. The un-bonded exposed sugar end is the 3' (3-prime) end
because this is the #3 carbon.

Describe the structure of the backbone of a DNA molecule.
Get your instructor’s initials before moving onward! _______
IV. Building a molecule of DNA:
A molecule of DNA contains two strands of DNA nucleotides held together by the hydrogen
bonds between complementary bases. We will now convert your single strand into a doublestranded DNA molecule by pairing the correct nucleotides.
1. Starting at the adenine end of your strand of nucleotides, attach the matching
nucleotide by joining their bases.
2. Add the base complementary to the next nucleotide in your strand (guanine).
3. Form a strong covalent bond between these new bases by linking their sugar-phosphate
backbones.
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4. Continue until all the bases in your original strand have partners.
Note that the 3' end of one side is opposite the 5' end of the complementary side. The two
backbones are equidistant from one another but run in opposite directions.
V. DNA Replication:
DNA Replication requires that the two nucleotide strands of the molecule be separated from
one another, then that new nucleotides be brought in and paired with the existing bases. This
is accomplished by an unwinding enzyme that first travels along the DNA molecule breaking the
hydrogen bonds between the bases. This allows another enzyme, DNA polymerase, to attach
to each side of the open DNA and travel along pairing new nucleotides with the existing strand
and bonding the new sugars and phosphates to make a backbone. DNA polymerase always
travels from 3' toward 5' of the existing (old) strand, pairing nucleotides in sequence.
For this part of the exercise, you will need the 12 extra nucleotides you put aside earlier to build
the new nucleotide strands.
1. Pull the two sides of your DNA molecule apart from one another to a distance of about
30 cm.
2. Starting at the 3’ end of each nucleotide strand, pair each nucleotide (one at a time in
order, just like it happens in the cell!) with its complementary base.
3. As you create a pair, bond its phosphate to the sugar of the one added just before it,
working down the chain in order.
Each molecule of DNA produced by this process contains “old” bases on one side and “new”
bases on the other. This is referred to as semi-conservative replication. You don’t end up with
one old strand and one new one, but two strands that are each half old and half new.

What enzyme in DNA replication are you acting as when you are replicating the DNA?

The old DNA is read from 3’ to 5’. In what direction is the new strand of DNA nucleotides
made during DNA replication?

Compare the sequence of bases on the two strands within one of the DNA molecules
produced by DNA replication.

Compare the sequence of bases between the two separatemolecules of DNA resulting from
replication.
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
At this point in the cell cycle, there would be two strands of DNA held together by a mass of
protein at the centromere. When these two strands condense during cell division, they will
become visible as sister chromatids (in a duplicated chromosome).
VI. Repeat DNA Replication:
Don’t destroy your DNA yet! Let’s take a minute to see what happens in the case of a mutation.
1. Break one of your DNA molecules down to its nucleotides.
2. Borrow a nucleotide from another group of students and substitute it for one in the
middle of your right half of the remaining DNA molecule. Make sure that this nucleotide
is different from the one that was previously in that spot!
Notice how the puzzle doesn’t fit together correctly at the point of your substitution. If you
were working with real DNA, a tiny “bubble” would form in the strand. Occasionally, DNA
polymerase makes mismatch errors as you have just demonstrated. Normally, a proof-reading
enzyme corrects these mistakes before replication occurs again. What happens if the
proofreading enzyme doesn’t do its job?
3. Complete replication of your strand (as you did in part V.) without correcting the
mismatch error (borrow another nucleotide if necessary).

List the DNA sequence of the left side strand of each the two DNA molecules
produced by replication of the DNA with the mismatch error.
DNA molecule 1:
DNA molecule 2:

Compare these two sequences. Is a mutation found in both the DNA strands resulting
from DNA replication? Explain your answer.
The change in DNA sequence that you have simulated represents a mutation. Mutations can
result from uncorrected mismatch errors, but can also form as the result of environmental
factors like exposure to UV light, radiation and chemicals and the production of free radicals by
the cell.
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Exercise 2. DNA Extraction: Although we cannot see individual molecules of DNA at the
molecular level, we can isolate large quantities of DNA by breaking open large numbers of cells.
The goal of this laboratory exercise is for you to see, touch and feel DNA. Scientists in
biotechnology and research laboratories perform essentially the same technique you are
performing today to study DNA in action.
“Extracting DNA from bodies is incredibly easy, so easy you can do it in your kitchen.
Take a handful of tissue from some plant or animal – peas, steak or chicken liver. Add
some salt and water and pop everything into a blender to mush up the tissue. Then add
some dish soap. Soap breaks up the membranes that surround all of the cells that were
too small for the blender to handle. After that, add some meat tenderizer. The meat
tenderizer breaks up some of the proteins that attach to DNA. Now you have a soapy,
meat-tenderized soup, with DNA inside. Finally, add some rubbing alcohol to the mix.
You’ll have two layers of liquid: soapy mush on the bottom, clear alcohol on top. DNA
has a real attraction to alcohol and will move into it. If a goopy white ball appears in the
alcohol, you’ve done everything right. That goop is the DNA.”
–Neil Shubin, Your Inner Fish
How this procedure works:
1. Mashing: this process breaks down the cell walls of the fruit
2. Extraction solution: this solution contains detergent and salt and water.
A. The detergent breaks down membranes.
What cell membranes need to be broken to release DNA?
B. DNA carries a negative charge and is therefore very soluble in water, so when the
cells are broken open, the DNA goes into solution.
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C. The salt (NaCl) breaks down into ions in the water. Positively charged sodium ions
(Na+) are attracted to and bind the negatively charged DNA molecules. This makes
the DNA molecules neutral, so they clump together.
3. Ethanol: DNA is not soluble in ethanol. When ethanol is added to the solution, the DNA
can no longer stay in solution and forms a precipitate.
Procedure:
1. Mashing the fruit:
a. Obtain a strawberry. Remove the green part.
b. Place the strawberry in a seal-able plastic bag labeled with your group’s name.
c. Squeeze out any extra air and seal the bag.
d. Place the bag on the counter and use the heel of your hand to thoroughly smash
the strawberry.
2. Add a volume of DNA extraction solution equal to the volume of strawberry already in
the bag. The less extraction medium, the more DNA you will extract, but too little and
the experiment won’t work.
3. Reseal the bag and place it into a hot water bath.
4. Let the mixture sit in the water bath for 15 minutes.
5. Transfer the bag to your ice water bath for 5 minutes.
6. While your DNA extraction is cooling, set up the filtration system. Place a funnel over a
clean 500 ml beaker. Insert a coffee filter into the funnel.
7. Pour your cooled extraction solution (liquid only) into your filtration system and allow it
to drip through into the beaker. It may take several minutes for all the liquid to pass
through the filter.
8. Dispose of the bag and fruit debris in the garbage can.
9. When filtration is complete dispose of the coffee filter in the garbage can.
10. Swirl the solution in your beaker. Immediately after swirling, transfer the filtrate into a
test tube to a depth of 2-3 cm.
11. Carefully pour a layer of about the same amount of cold ethanol on top of your filtrate
in the test tube. The ethanol must be very cold, so be sure to keep it on ice at all times!
12. Let the solution sit for 2 minutes.
13. A clear gelatinous precipitate (snot) will form between the alcohol layer and the water
layer (extraction solution). The white stuff is clump of DNA from the cells of the
strawberry. Use a plastic loop to drag the DNA up the side of the test tube and into a
watch glass. It’s safe to touch, so feel free to check it out!
14. Clean up! All materials in this laboratory can be disposed of in the garbage or down the
sink
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Analysis:
A similar procedure can be used to extract DNA from your own cheek cells! In what ways would
human DNA be like the DNA you just extracted from strawberry?
Your precipitated DNA contains both nucleic acids and proteins. Where do the proteins come
from? (Hint: Think about how DNA is arranged inside a cell.)
The nucleus of every human cell contains approximately 2 meters of DNA. A typical adult human
contains 60 trillion cells (60,000,000,000,000). The distance from the Earth to the Moon is
380,000 km. If the DNA of a single human were laid end to end, how many times would the
strand go to the moonand back?
Exercise 3. Protein Synthesis: This exercise is a continuation of the DNA puzzle you worked
through in exercise 1. You may not get to this exercise or all the way through it in today’s lab.
DNA puzzles will be available in open lab if you need more time.
Genetic material that is passed from one generation to the next is contained within the
molecules of DNA. DNA codes for specific genetic traits by directing the manufacture of
proteins through the processes of transcription and translation. During transcription the codes
of bases on the DNA molecule are copied onto a molecule of messenger RNA (mRNA). During
translation the bases on the mRNA are converted into a sequence of amino acids through the
action of transfer RNA (tRNA).
We will use a DNA puzzle kit with cardboard pieces to model the conversion of the message in
DNA into a strand of RNA that can leave the nucleus and then convert the RNA into a short
chain of amino acids. In order to understand these events, it is important to work both with the
correct pieces and assemble them in the order described. Resist the temptation to skip steps.
Your team will need the following color-coded pieces:
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12 Deoxyribose units (dark pink)
12 Ribose units (light pink)
24 Phosphate units (yellow)
4 Adenine (A) units (light green)
2 Thymine (T) units (light blue)
2 Uracil (U) units (white)
8 Cytosine (C) units (dark green)
8 Guanine (G) units (dark blue)
Ignore the large paper sheet and any other parts of the puzzle for now.
I. RNA Nucleotides:
1. Compare a deoxyribose unit to a ribose unit by looking at the structural formula for
each molecule as printed on the cardboard.
2. Examine the uracil unit. Find another puzzle piece that is similar in appearance to uracil.

Describe the structural differences between ribose and deoxyribose.

What part of a nucleotide does uracil represent? What does it “replace” in RNA?
II. Transcription:
During transcription, the two strands of DNA are separated along a portion of the molecule.
This region to be transcribed is a gene. Only one side of the molecule, called the sense strand
will be transcribed. The complementary side, often called the anti-sense strand, will remain
inactive. To model transcription, we will first form the sense strand, but we will ignore the antisense strand, simply remembering that it would be present in complete DNA.
1. Use deoxyribose to form the following DNA nucleotides: 2 adenine, 6 cytosine, 2
guanine, and 2 thymine.
2. Use ribose to form the following RNA nucleotides: 2 adenine, 2 cytosine, 6 guanine, and
2 uracil.
Make sure you know how to distinguish between DNA nucleotides and RNA nucleotides before
you move on!
3. Lay the sheet of plastic from the puzzle kit on your bench.
4. Build a strand of DNA in the following sequenceon top of the plastic.
3’-CGTCCACGTCCA-5’
If you don’t recall what 3’ and 5’ stand for, review to exercise 1
5. Start at the 3’ end of your strand of DNA nucleotides.
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6. Add the complementary RNA nucleotide to the first base (at the 3’ end of the DNA
nucleotide strand)
7. Add the next complementary RNA nucleotide and form a covalent bond between these
first two nucleotides by connecting the phosphate of the second nucleotide to the sugar
of the first nucleotide.
8. Continue pairing down the DNA and link together the RNA sugar/phosphate backbone
to make a strand of RNA.
9. When the RNA is complete, slide the DNA off the plastic sheet and out of your
workspace. Don’t dismantle it yet! You’ll want to be able to go back if you made a
mistake!
An enzyme, RNA polymerase, assists the pairing and catalyzes the bonding to form a backbone.
In the cell, once the RNA strand is completed and the RNA separates from the sense strand, the
DNA zips back up reforming the double helix.

Describe how transcription differs from DNA replication.

How does the RNA molecule produced by transcription differ from the DNA molecule
that it was made from?
III. Types of RNA:
Eukaryotic cells contain three types of RNA: ribosomal (rRNA), transfer (tRNA) and messenger
(mRNA). All are produced by transcription of DNA, but of different portions of the DNA
molecules. Ribosomal RNA combines with proteins to form bodies called ribosomes. The
ribosomes are located in the cell's cytoplasm and are the organelles where protein is initially
produced. Transfer RNA bonds to amino acids in the cytoplasm and transports them to the
ribosomes where it pairs with messenger RNA to put amino acids into specific sequences.
Messenger RNA carries the instructions for protein synthesis (the genetic code) from the
nucleus into the cytoplasm and to the ribosomes.
Look at the RNA molecule you just built and the pieces of the puzzle that you haven’t used yet.
These pieces represent the three types of RNA. Determine which pieces represent which type
of RNA. Describe those pieces in this table.
Type of
Description of puzzle piece(s)
RNA
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mRNA
tRNA
rRNA
IV. Messenger RNA and the Genetic Code:
In the next step, the base sequence in the RNA will be read three-at-a-time in order with no
skips or overlaps. Each three-base triplet of nucleotides is called a codon and serves as the
code for a specific amino acid placed into position in a protein being assembled. Thus, each
RNA codon is complementary to a DNA codon. Table 1 lists the RNA codons and the amino acid
specified by each different codon. The RNA codons are read from the 5' toward the 3' end of
the RNA molecule.
Use table 1 to determine which amino acids are specified by the RNA strand you assembled?
_________________, _________________, _________________, _________________
Table 1: The Genetic Code:RNA codons for amino acids used in protein synthesis. Full
names and three-letter abbreviations for each amino acid are provided.
First
Second Base
Base
U
C
A
G
Phenylalanine
Tyrosine
Cysteine
U
(Phe)
Serine
(Tyr)
(Cys)
(Ser)
Leucine
Stop
Stop
(Leu)
Tryptophan
(Trp)
Histadine
C
Leucine
Proline
(His)
Arginine
(Leu)
(Pro)
(Arg)
Glutamine
(Gin)
Asparagine
Serine
Isoleucine
A
Threonine
(Asn)
(Ser)
(lle)
(Thr)
Lysine
Arginine
Methionine (Met)
(Lys)
(Arg)
Aspartate
Alanine
(Asp)
Glycine
Valine
G
(Ala)
(Gly)
(Val)
Glutamate
(Glu)
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Third
Base
U
C
A
G
U
C
A
G
U
C
A
G
U
C
A
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V. Translation:
Now we will use the remaining pieces in your puzzle kit to simulate the process of translation.
1. Open the ribosome placemat from your kit and place it on your desk.
The placemat contains the outline of a ribosome. The large subunit is labeled 60S and the small
subunit is labeled 40S. The A site and the P site are locations where activated tRNAs align their
anticodons with complementary RNA codons.
2. Find the tRNAs in your puzzle kit (the large pieces in orange or brown) and the small
glycine and alanine activating pieces (in the same colors).
In the cell, tRNAs are activated when an activating enzyme attaches the appropriate amino acid
to the tRNA.
3. Assemble active tRNA molecules by adding the appropriate activating piece and amino
acid to each tRNA.
Notice that the top of your tRNA (when the writing is right-side up) is “bumpy”. These bumps
represent the position of the anticodon. Different tRNAs have different anticodons and carry
different amino acids. During translation, the anticodon binds to complementary codons on the
RNA molecule. The requirement of matching codon to anticodon determines the specificity of
translation.
4. Keeping your mRNA on the plastic sheet, align the 5’ end of your mRNA molecule to the
5’ end labeled on the placemat.
5. Move activated tRNAs in and out of the P site of the ribosome until you find one that is
complementary to the first codon of your RNA (the notches and bumps fit together).
6. Repeat the process to find a tRNA that is complementary to the second codon of the
RNA (in the A site).
When the A site and the P site are full, you are ready to make a bond between the amino acids.
In the cell, the enzyme action of rRNA carries out this chemical reaction. This is where things
get a bit complicated, so take your time!
7. Remove the amino acid attached to the tRNA in the P site and attach it to the exposed
end of the amino acid in the A site. Attach the one on the right to the one on the left.
The result of this reaction is a peptide bond between the first two amino acids of your protein.
8. Keeping the tRNA in the A site attached to its RNA codon, move the entire puzzle to the
right one spot.
At this point, you should have one codon outside and to the left of the ribosome on your
placemat. Your second codon and its matching tRNA (carrying the growing protein) should be in
the P site. The A site will lack a tRNA. The tRNA that used to be in the P site is released from the
ribosome and is free to be reactivated in the cytoplasm.
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9. Find the tRNA that is complementary to the third codon in your RNA and place it in the
A site.
10. Form a peptide bond between the second and third amino acids in your protein by
removing the two-amino acid chain from the tRNA in the P site and attaching it to the
amino acid in the A site.
11. Move the RNA down one more spot.
12. Repeat these steps one more time and you will have built the protein encoded in your
mRNA!

What are the roles of tRNA and their anticodons in the process of translation?

Determine the matching anticodons for the following codons:
Codon
Matching Anticodon
AUG
GUU
CAG

Explain how translation differs from transcription.
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Applying What You’ve Learned

Scientists use the term “anti-parallel” to describe the two strands of nucleotides that form a
DNA molecule.Consider the meaning of the terms “anti” and “parallel” and to explain how
the term anti-parallel applies to DNA.

The connections between the sugar and the phosphate and between the sugar and the base
of a nucleotide fit together like “lock and key” in this puzzle. The bases, however, just slide
together (and apart) easily. How does this arrangement in the puzzle reflect the actual
properties of these connections in a DNA molecule?

How does a mismatch error differ from a mutation?

Biologists use a variety of chemicals to explore the processes of transcription and translation
in cells. Suppose a scientist treated a cell with a chemical that inhibits transcription. Would
translation be able to occur? Why or why not?

The method we used to extract DNA from a fruit is the same method that would be used to
extract DNA from human cells. Suppose we took a sample of your blood. Describe in detail
how we would extract DNA from your blood cells?
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Date Due:
Name:
Pre-lab 5: DNA Fingerprinting
To prepare for this laboratory read about restriction enzymes and gel electrophoresis in section
16.7 of your textbook and DNA fingerprinting in section 16.2.
1. In your own words, define each of the following terms:
Restriction enzyme:
Gel electrophoresis:
RFLP analysis:
Plasmid:
2. A. Use your textbook (Chapter 5) and/or the Internet to determine the overall electrical
charge of a molecule of DNA.
B. Explain how the charge of DNA is relevant to this week’s lab.
3. Most of the solutions we use in this week’s lab will be dispensed in microliters. How big
(or small) is a microliter? How would you describe the volume of this much solution to
someone?
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Name:
Lab 5: DNA Fingerprinting
By the end of this lab, you should be able to:
 Describe how and where the DNA of different individuals differs.
 Explain the origin and function of restriction enzymes.
 Describe the process of agarose gel electrophoresis.
 Explain how DNA fingerprinting can be used to differentiate between individuals.
Exercise 1. DNA Fingerprinting:All individuals (except identical twins) have unique DNA
sequences. As we will soon learn in lecture, this uniqueness is a result of meiosis and sex. Using unique
DNA sequences to identify paternity, criminals, or unidentified bodies has become common place in
our society. To examine the unique DNA sequence of an individual, scientists cut DNA samples using
restriction enzymes. These enzymes cut DNA only when they find a specific sequence of nucleotides.
Different types of restriction enzymes cut DNA at different sequences of nucleotides. Since different
people have different DNA sequences, restriction enzymes cut different people’s DNA in different
places. The result is a mixture of small pieces (or fragments) of DNA of different sizes. These DNA
fragments can be separated by size and visualized with a process known as agarose gel
electrophoresis. The result is ladder-like set of “bars”. The pattern of the bars is unique to the person
whose DNA was used. This pattern is known as a person’s DNA fingerprint.
The procedures for this lab is complex and we will approach it in four steps; practice, adding loading
dye, gel loading, and staining. You will work in groups of four.
A. Practice: Your instructor will demonstrate the use of a micro-pipetteman and the process of
loading a gel before distributing a tube of practice dye (PD) and a practice gel.
1. Set your pipetteman to 15 microliters and add a tip. Everyone in your group will use the same
tip.
2. Use the pipetteman to suck up 15 microliters of practice dye.
3. Cover your practice gel with a layer of water. The water should be deep enough that its surface
is smooth.
4. Slowly drop the dye into the well as described by your instructor.
5. Everyone in your group should load at least one well on the practice gel. After everyone has
practiced, throw the PD tube in the garbage; pour the water off the gel and dispose of the gel
and its container in the garbage.
B. Adding loading dye: Your instructor will provide you with a set of six DNA samples and a tube of
loading dye (LD). One DNA sample is from the crime scene (CS) and the others are from suspects (S1
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through S5). Be careful not to confuse the LD tube with the PD tube from the practice exercise (that’s
why we asked you to throw the PD tube away!).
1. Set your pipetteman to 5 microliters and add a tip. We will attempt to conserve tips in this
step, but if the tip ever touches the side of a tube containing a DNA sample, you must throw it
away to prevent the contamination of other DNA samples.
2. Suck up 5 microliters of dye from the LD tube. Add the dye to each of your DNA samples by
holding the tip over the top of the tube while ejecting the solution. A drop will form on the tip.
Touch the drop to the side of the tube (without the tip touching the side) to transfer the drop
to the side of the tube. Close the tube.
3. After adding LD to each of your DNA samples take them to the microfuge on the instructor’s
bench. Place your tubes in the microfuge directly across from each other (the microfuge must
be balanced to work properly). Use the “Pulse” button to spin your samples for about 5
seconds. When you pull them out, the DNA and the LD will have mixed at the bottom of the
tube.
C. Gel loading: Your instructor will provide you with an agarose gel, a gel rig and a bottle of 1X TAE.
1. Place your agarose gel in the electrophoresis apparatus. Make sure the wells of the gel are
near the black electrode.
2. Place the electrophoresis apparatus near the power source that you will be sharing with the
other team at your lab bench. Be sure that the cables on your apparatus reach the power
source as you cannot move the gel once the samples have been loaded.
3. Add enough 1X TAE to cover the surface of your agarose gel. The solution should fill the wells
on both sides of the gel and cover the gel. The surface of the solution should be smooth. Check
with your instructor before continuing.
4. Set your pipetteman to 20 microliters.
5. Using a different tip for each sample, load you DNA samples into the gel. To help with
orientation, load the CS sample into the first lane, skip a lane and then place your suspects in
order in the remaining lanes.
6. Carefully slide the cover onto the electrophoresis apparatus and plug your gel into the power
source. When the other team using your power source has attached their gel, turn on the
power to high. If everything is set up correctly, you should see tiny bubbles streaming up the
short sides of the apparatus.
7. Allow the gel to run for approximately 45 minutes. You will know it is done when the low
band of stain (light blue) crosses the red strip on the gel apparatus.
D. Staining:We obtain the best results when we stain the gels overnight. Your instructor may chose
to do a quick stain if sufficient time remains in your lab.
1. Turn off the power source and unplug your gel apparatus. Slide the top off of the gel
apparatus.
2. Obtain a staining tray. Use a piece of tape to label the tray with your group’s initials and your
instructor’s name.
3. Lift the tray containing your gel out of the gel apparatus.
4. Use your finger to gently slide the gel off of the tray into the staining tray.
5. Pour 1X Fast Blast DNA stain over your gel until it is completely covered.
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6. Cover the staining tray with saran wrap and put it on the back counter for your instructor to
store.
Exercise 2. Understanding DNA fingerprinting: When you return to lab next week, you
will look at the result of the agarose gel electrophoresis of your DNA samples. It might be
difficult to understand what you are seeing. The goal of this exercise is to show you how this
type of DNA fingerprinting works.
To understand this exercise, we first have to understand one of the “shortcuts” scientists use to
discuss DNA. When using the method we are using in this lab for DNA fingerprinting, the
specific DNA sequence of an individual is not examined, rather the size of pieces of DNA
produced by restriction enzymes. One way of measuring DNA size is to determine how many
base pairs it contains. Figure 1 diagrams a short fragment of DNA. Remember that DNA has two
sugar phosphate backbones where nucleotides are attached to each other by covalent bonds.
The two resulting strands attach to each other with hydrogen bonds between their bases. The
two bases together are called a base pair (bp).
Figure 1:DNA fragment with numbered base pairs (bp).
Numbered
Base Pairs
Sugar Phosphate
Backbone
1
2
3
4
5 6
7
8
9
10 11 12
DNA Fragment Length = 12 bp
When discussing “pieces” of DNA, scientists will name them by the number of base pairs they
contain. In figure one, the base pairs are labeled sequentially from left to right (much like mile
markers on a highway). The piece of DNA we see here has a size of 12 bp. As we have already
learned in this lab, restriction enzymes cut different people’s DNA in different places and that
produces pieces of DNA that are different sizes. We can more clearly talk about these
fragments by assigning them sizes (counting the number of bp that they contain).
The DNA samples we used for this lab actually come from bacteria. Bacteria contain small
circles of extra DNA called plasmids. Plasmids generally contain only a few genes, but are
designed to have unique sequences that are recognized by specific restriction enzymes. Unlike
eukaryotic DNA, the DNA of prokaryotes is circular. Whereas linear DNA fragments have their
base pairs counted from left to right, scientists have to choose a starting point for counting in
the circular chromosome of a bacterium. The origin is a randomly chosen location on the
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plasmid where we start counting. It represents both zero point, but also the total number of
base pairs in the plasmid. The origin is, generally, not cut by any restriction enzymes.
Figure 2 contains a map of the fictional plasmid pBIO. The origin is marked on the map as well
as several labels followed by base pair numbers. This plasmid is 8692 base pairs from the origin,
all the way around the plasmid and back to the origin. The labels representthe number of the
specific base pair where the adjacent sugar phosphate back bone is cut (the restriction
site).Keep in mind that a restriction site represents the sequence of DNA recognized by the
enzyme, but the enzyme only cuts the DNA once on each of the two sugar-phosphate
backbones. So, the enzyme BamH1 recognizes a region around both 1246 and 7952 bp from
the origin and cuts specifically at those base pairs.
Figure 2: Map of pBIO plasmid.
Origin (both 0 bp and 8692 bp)
EcoRI at
8603 bp
BamHI at
7952 bp
BamHI at
1246 bp
pBIO
8692 bp
HindIII at
1481 bp
HindIII at
4793 bp
In this exercise, we will predict what an agarose gel would look like if it contained the plasmid
pBIO cut up by each specific enzyme on the map, individually, and by a combination of all three
restriction enzymes listed at the same time.

Before we begin, return to Figure 1. Imagine that a restriction enzyme cuts that
fragment at base pair 3. How big would TWO resulting DNA fragments be?
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Procedure:
1. Separate this the last two pages of this lab from your packet and turn the manual so
that Figure 2, the map of the pBIO plasmids is showing.
2. Work through the questions below to determine the size of the fragments produced by
each restriction enzyme (and all three together).Make sure you show all of your work
so that your instructor can help you if you get stuck or have an incorrect answer.

How many fragments would you expect to see on a gel if you digested pBIO with BamHI? What
size is each fragment? Show your work!

How many fragments would you expect to see on a gel if you digested pBIO with HindIII? What
size is each fragment? Show your work!

How many fragments of DNA would you expect to see on a gel if you digested this plasmid with
EcoRI? What is the size of each fragment? Explain your answer
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
How many fragments of DNA would you expect to see on a gel if you digested this plasmid with
BamHI, EcoRI and HindIII? What is the size of each fragment? Show your work!
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3. Now that we have determined the size of the DNA fragments produced by each restriction enzyme
digestion, we can predict what the agarose gel will look like. Use your answers on the previous page
to “build” your gel. Remember:
o
o
o
o
The DNA loaded into a particular lane travels vertically from the wells to the bottom of the gel.
Each different sized DNA fragment produced by a restriction enzyme digest is represented by a
unique bar in that lane of the gel.
DNA fragments placed in an electrical field separate by size with large fragments staying close to
the well and smaller fragments traveling down the gel.
Two fragments of the same size in different lanes will travel the same distance on the gel.

Indicate, on the gel below, how you would orient the positive and negative poles of the electric field
in order to separate the DNA fragments.

Don’t forget this question!
You load the gel as follows:
Lane 1: pBIO treated with EcoRI
Lane 2: pBIO treated with BamHI
Lane 3: pBIO treated with HindIII
Lane 4: pBIO treated with EcoRI, BamHI, and HindIII
Draw a picture of the gel you would expect to see. Label each fragment with its size (write the size on
or next to the bar you draw in the gel).
1
2
3
4

In the DNA fingerprinting lab, you will use electrophoresis of DNA to figure out “whodunit”. Explain
how you will use your agarose gel to make this determination.
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Now that you understand how DNA fingerprinting works, answer the three questions on the next page.
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Racie and John had Tyler in 2009. Two years later, the couple decided to separate. Soon after their separation,
Racie discovered she was pregnant again. John denies that he is the father of Racie’s second child because he
knows Racie started dating Steve soon after the separation. To determine who should pay child support, a
paternity test is performed. Blood samples are collected from each member of the family and also from Steve. The
DNA is digested with a combination of restriction enzymes and the fragments are separated by gel electrophoresis.
The gel is depicted below.
Racie
John
Tyler
Baby
Steve

From this information, can you make a guess as to who is the father of Racie’s second baby? Explain
your answer.

If the DNA fingerprint of Racie’s first son, Tyler, was not provided on the gel, would you be able to
determine the father of Racie’s baby? Why or why not?

What exactly does a DNA fingerprint represent?
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Applying What You’ve Learned:

Why do scientists tend to focus on the non-coding “junk” DNA when performing DNA
fingerprinting?

Explain why restriction enzymes produce different sized DNA fragments from the
isolated DNA of different people.

Examine the following agarose gel from a Biology 102 student. Based on this gel, which
suspect most likely committed the crime?
Crime
Scene
Suspect Suspect Suspect Suspect Suspect
1
2
3
4
5

Explain, based on what you learned about DNA variability and agarose gel
electrophoresis, why this suspect is the most likely criminal.

Examine your gel after staining. Which suspect most likely committed the crime?
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Date due:
Name:
Pre-lab 6: Meiosis
1. Review:
A. When does DNA replication take place in the cell cycle?
B. Briefly summarize the process of DNA replication.
C. Diagram a duplicated chromosome. Be sure to label the sister chromatids and the
centromeres.
2. Briefly define the following terms in your own words. Remember that copying definitions
from any published resource or website or from another student is plagiarism!
Chromosome:
Haploid:
Diploid:
Gamete:
3. What role does meiosis play in the life cycle of an organism?
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Turn over!
4. Complete the following chart comparing meiosis and mitosis:
Mitosis
Does the cell go through the
cell cycle?
Does the cell go through DNA
replication? How many times?
How many times does
cytokinesis occur?
How many cells are produced
by the entire process?
Does the final number of
chromosomes in the cell
change?
Does the DNA sequence of
the cell as a whole change
during the process?
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Meiosis
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Name:
Lab 6: Meiosis
By the end of this lab, you should be able to:
 Differentiate between the two types of cell division
 Describe what happens during each phase of meiosis
 Use chromosome models or drawings to explain the process of meiosis to another
student
 Explain how crossing over increases genetic diversity
 Explain why sex is important to evolution
Exercise 1: Modeling Meiosis with Play-Doh©:In this exercise you will be modeling the
movement of chromosomes through the eight phases of meiosis. Recall that we learned that
humans have 23 different types of chromosomes and each of your cells (except sperm or egg
cells) have two versions of each of these chromosomes for a total of 46 in each cell. This is a
result of the way that humans reproduce. For every type of chromosome you have two
versions, one inherited from your father and one inherited from your mother. Scientists use the
term diploid to describe this situation where there are two versions of each chromosome. In
sperm or egg cells the situation is a little different. If these cells had 46 chromosomes then
when they fused the resulting cell would have 92 chromosomes, clearly this is not what
happens.
When your bodies produce these sex cells they use the process of meiosis to reduce the
number of chromosomes from two of each type to one of each type. Cells with one of each
type of chromosome are called haploid. Meiosis involves two cell divisions. During the first
division, homologous chromosomes are separated and two cells are produced. This is the step
of meiosis that actually reduces chromosome number. During the second division of meiosis,
sister chromatids separate and each cell divides producing a total of 4 cells. This step is most
similar to mitosis.
Throughout this exercise you will focus on changes and movements in the DNA of a dividing
cell. Remember that meiosis involves a spindle apparatus and centrosomes just like mitosis. As
you work, recall the movements of these structures and other morphological changes that
occur in the cell. Your textbook and laboratory manual contain diagrams that will help you line
up your chromosomes correctly in the cell. Answer the questions in the text as you perform
each exercise.
To help you visualize meiosis, it is important that you complete each step in order.
Check to make sure you following each step completely before moving on .
Set up and Interphase:You will model meiosis in a cell with a diploid number of 4 (2n =4).
 How many pairs of homologous chromosomes will be in your cell?
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
How many total chromosomes will be in your cell?
1. Build four duplicated chromosomes out of thick “snakes” of Play-Doh© as follows:
 Color 1, long
 Color 2, long
 Color 1, short
 Color 2, short
Before you move on, answer these questions:

Which Play-Doh© color represents chromosomes from Mom?

Which Play-Doh© color represents chromosomes from Dad?

Who are your long chromosomes inherited from?


Who are your short chromosomes inherited from?


Circle one: mom / dad / one from mom and one from dad
Circle one: mom / dad / one from mom and one from dad
Which of the following constitute(s) a homologous pair (check the appropriate box[es])?
 Long, blue, duplicated chromosome and long, yellow, duplicated chromosome
 Long, yellow, unduplicated chromosome and long, blue, unduplicated
chromosome
 Long, blue, duplicated chromosome and short, blue duplicated chromosome
 Short, yellow unduplicated chromosome and long yellow unduplicated
chromosome
2. Interphase: Use chalk to draw a large circle your desktop to represent your cell. Draw a
second circle inside to represent the nucleus. Pile your chromosomes randomly in the
nucleus.
 What stage of interphase is represented by your pile of chromosomes? How do you
know?

How many times was all the DNA in your cell replicated to reach this stage?
3. Meiosis I:
A. During prophase I, the chromosomes condense and become visible by light microscopy.
Homologous pairs of chromosomes find each other. Because each chromosome
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contains two sister chromatids, the homologous chromosome complex contains four
strands and is called a tetrad.
NOTE: DO NOT PERFORM CROSSING OVER AT THIS TIME! WAIT FOR EXERCISE 2!
a. Form tetrads with each pair of homologous chromosomes in your cell. The tetrads
should be randomly arranged in your cell.
b. Erase the nuclear envelope

Which is stronger? The bond between the sister chromatids in your tetrad or the
bond between homologous chromosomes in your tetrad?
c. Draw a spindle apparatus with several spindle fibers extending from pole to pole.
Note that this is not the way that the spindle apparatus forms in the cell (they
actually grow out to the tetrad from each pole), but it will help us visualize how the
chromosomes move.
d. Arrange the tetrads randomly throughout the cell so that each tetrad is on a
separate pair of spindle fibers. Your tetrads should not be lined up at the spindle
equator (yet!).
B. Represent metaphase I by moving the tetrads along their spindle fibersto the spindle
equator of the cell. The side of each chromosome should face the spindle poles.
C. During anaphase I, homologous chromosomes are separated. To represent Anaphase I,
move the members of your tetrads apart. The centromeres of the chromosomes do not
split, but the two chromosomes of the tetrad are separated.

How does meiosis I differs from mitosis?
D. To represent telophase I, move the separated homologous chromosomes to opposite
ends of the cell.

How many cells are formed by meiosis I?

How many chromosomes are in each cell?

Is the resulting cell diploid or haploid?
E. Cytokinesis (either by cell furrowing or cell plate formation) separates the cell into two
daughter cells. Erase your original cell and draw a large circle around each cluster of
duplicated chromosomes to represent two cells side-by-side.
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1. Meiosis II: Depending on cell type, there may be a brief break between meiosis I and II.
During this break, chromosomes may unwind, but DNA replication will not occur again.
A. To represent prophase II, pile the chromosomes in the center of each cell.
B. Align individual chromosomes along the spindle equator to represent metaphase
II.

How is the arrangement of chromosomes in metaphase II different from the
arrangement of chromosomes in metaphase I?
C. To represent anaphase II, separate the sister chromatids of each chromosome and
pull them slightly toward opposite poles.
D. In telophase II and cytokinesis, the sister chromatids move to opposite poles of the
cell and each cell divides into two.

How many cells does Meiosis II produce?

Are the resulting cells haploid or diploid?

How is Meiosis II similar to mitosis?
That’s meiosis! Go through the process a couple more times and then model it for your
instructor. Get your instructor’s initials before moving on:
Exercise 2. Modeling Meiosis with Crossing-Over: The process of crossing-over creates
new combinations of alleles. When crossing over occurs, the non-sister chromatids of a
homologous pair must exchange genetic material (bits of DNA) during prophase I of meiosis.
Does the last sentence make sense to you? Think it through and get help if you don’t
understand!
Crossing over must occur at least once in each homologous pair. The regions in which crossing
over occurs actually hold the homologous chromosomes together! Since chromosomes contain
thousands of genes, however, the chance of any particular gene being affected by crossing over
is quite low. When we study genetics, we will find that offspring containing combinations of
alleles that result from crossing-over are less frequent than offspring containing combinations of
alleles that are produced when crossing over does not occur.
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1. To model meiosis with crossing-over, repeat Exercise 1.
2. During prophase 1, break off the ends of one of the sister chromatids that form each of
your long chromosomes. Reattach the pieces you broke off to the other member of the
homologous pair. As a result, your long chromosomes should each have one “leg” that
contains two colors of clay. Once you’ve completed crossing over, go through the rest of
meiosis.

Explain how the gametes produced during meiosis with crossing-over are different than
the gametes produced during meiosis without crossing-over.
Exercise 3. Why Sex?:This video explains why sexual reproduction is important to the
survival of the species. It ties together many concepts that we will cover during the rest of the
term including sexual reproduction, genetics and evolution. Reading the questions before you
begin will make it easier for you to answer them!
1. What process do most species used to pass on their genes?
2. Was black spot disease in minnows more likely to infect asexual or sexual reproducers?
Why?
3. What did researchers do by moving fish from a lower pond into the pond where sexually
reproducing fish were being attacked by black spot disease?
4. List one benefit of sexual reproduction.
5. What do peahens look for in the tails of prospective mates?
6. In terms of evolution, why was it beneficial for peahens to mate with males with better
tails?
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7. In what type of familial situation does monogamy become important?
8. In the monogamous society of songbirds, what is the benefit of cheating on your mate?
9. What caused gender role reversal in Jacana birds?
10. What environmental differences led to the different mating habits of chimpanzees and
bonobos?
11. What is an evolutionary psychologist interested in?
12. Why does Geoffrey Miller feel that humans evolved intelligence?
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Applying What You’ve Learned:

Differentiate between apair of sister chromatids and a homologous pair (you may want to
include a sketch!).

During what stage(s) of the cell cycle and/or meiosisare homologous pairs PRESENT in a
cell?

During what stage(s) of the cell cycle and/or meiosisare homologous pairs actually found in
pairs (tetrads) in a cell?

What happens to the number of chromosomes in a cell during meiosis? For example, if a cell
enters mitosis with 8 chromosomes, how many chromosomes are found in each daughter
cell produced by meiosis?

Describe at least 3 ways that sexual reproduction increases sexual diversity.
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Date Due:
Name:
Pre-lab 7: Genetics
1. Define the following terms in your own words:
Allele:
Heterozygous:
Homozygous:
2. Explain the difference between genotype and phenotype.
3. A. State Mendel’s law of independent assortment in your own words.
B. How many genes must you be studying for the law of independent assortment to apply?
4. You cross a true-breeding curly hair sheep to a true-breeding straight hair sheep. The sheep
have two curly hair offspring. Which allele is dominant?
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Name:
Lab 7: Genetics
By the end of this lab, you should be able to:




Explain the relationship between meiosis and genetics
Correctly use the terms genotype and phenotype to describe an organism
Predict the genotype and phenotype ratios in a given genetic cross
Explain the results of crosses using the concepts of segregation and independent assortment
Exercise 1. Cycles of Life Program 7.1 (Patterns of Inheritance): Answer the
following questions as you watch this short film:
1. Dr. Larson hand pollinates strawberry flowers and allows seeds to form. He then plants those new
seeds and grows the next generation. “The plants produced from these seeds are called the
generation.
2. When Mendel crossed two true-breeding stocks, he found that all of the offspring produced only
one visible trait. He named the trait that was apparent in the F1 generation a
trait. He identified the other one that did not occur in the F1generation as a
trait.
3. Mendel’s inherited factors are known to be genes. These genes are on structures that exist in the
nucleus called
. Genes that are responsible for different forms of a
trait are called
.
4. If the alleles in an individual are absolutely identical, then we call this
.
When there are two alleles in the same cell, but the alleles are different, we have a situation known
as
.
5. In peas, a trait such as tallness is governed by two alleles that
when
gametes are made.
6. Because each heterozygous parent has a dominant and a recessive allele, they can produce types of
gametes. This is the basis for the law of
7. Using
the
Punnett
Square,
.
we
can
depict
the
genotype
or
o
f
potential
offspring.
Genotypes
determine
the
physical
appearance,
or
o
f the resulting plants.
8. The cross between two heterozygous pea plants shown here produced tall and short plants in the
same
ratio obtained by Mendel.
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9. A dihybrid cross involves parents
offspring of such a cross display
for
traits…The
possible combinations of alleles. Again, the___
ratio, determined by independent assortment mimics Mendel’s observations.
Exercise 2. Introduction to Genetics. Punnett Squares and Probability:The
worksheet on the next page is designed to help you understand the relationship between
genetics and meiosis. You will also be introduced you the Punnett Square, a tool that many
students find useful when completing genetics problems. Remember that the best way to
understand genetics is to practice. Practice meiosis (Play-Doh is cheap!) and practice genetics
problems. Wait for class to complete! You will be bored if you do it ahead of time!!!

Complete the diagram by drawing the labeled chromosomes in each cell below(if you
just use letters, it is difficult for your instructor to check your understanding). As you
work, answer the questions in the middle of the diagram. Do not worry about crossing
over right now.
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Products of Meiosis I
Products of Meiosis II
(gametes)
Get your instructor’s initials before moving on!

What are all the possible genotypes of the gametes produced by parent one? Hint: Are
gametes haploid or diploid? How many letters represent a gamete?

What are all the possible genotypes of the gametes produced by parent two? Hint: Are
gametes haploid or diploid? How many letters represent a gamete?
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
In your own words, explain why an understanding of meiosis is necessary before you
begin genetics.

Complete this Punnett Square depicting the cross between a mother who is
heterozygous for gene A and a father who is homozygous recessive for gene A. Label
where the mother’s gametes are listed and where the father’s gametes are listed.

What do the genotypes listed in the boxes represent?

What is the ratio of genotypes you would get for the cross described in part A?
 Remember that a Punnett Square is just a prediction. Suppose a cross between these
individuals produces 600 individuals with the genotype Aa and 400 individuals with the
genotype aa. Do your results match your prediction? Explain.
Exercise 3. Observing Genetics in Plants: Your instructor will provide a
handout for this exercise.
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Exercise 4. Genetics Problems:The
primary difficulty students have with genetics
problems, or story problems in general, is that they don’t approach solving them in an organized
fashion. Poor problem solvers can become good problem solvers by practicing following a simple
organizational approach. This exercise is designed to introduce you to this approach. Don’t try to rush!
Complete each step before you move to the next. Do everything in order, even if it seems trivial. WRITE
EVERYTHING DOWN! The steps are not just busy work.
Problem A: In peas, yellow flower color is dominant to green. What colors and
proportions of offspring would result from a cross between a heterozygous
yellow plant and a homozygous green plant?
Step 1: Make a list of all of the information you have been specifically given in this problem.





What gene is being followed in this problem?
How many alleles exist for this gene?
What are the possible phenotypes?
Which allele is dominant?
What cross are you being asked to perform?
Step 2:List any additional information can you deduce from the problem.

Which allele is recessive?
Assign symbols to both alleles.


Choose a letter to represent the gene you are following:
Assign the dominant allele the capitalized version of that letter:
Phenotype:

Assign the recessive allele the lowercase version of that letter:
Phenotype:

Symbol:
Symbol:
What are all of the possible genotypes that can occur when there are these two
alleles in the population? List them in the table below and describe the
phenotypethat goes with each.
Genotype
Homozygous
dominant
Homozygous
recessive
Heterozygous
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
Is there anything else you can add?
Step 3:Use the information you’ve pulled from the problem (step 1) and what you have been
able to infer (step 2) to set up the cross.


Layout the cross you are asked to perform in terms of both phenotypes and genotypes.
Complete the first two rows of the table below.
Determine the genotypes of the gametes each parent can produce (third row of the
table below). Since a gamete gets one copy of the gene, each gamete genotype will have
only one of the alleles in the parent plant’s genotype.
Parent A
Parent B
Phenotype
Genotype
Possible
Gametes
Determine the possible genotypes of the offspring that could be produced by these parents.
You can either think this through or use a Punnett Square. For this example, we’ll use a Punnett
Square.
a. To create the Punnett Square create a box with:
o One row for each of the different gamete genotypes from one parent.
o One column intersecting the rows for each of the different gamete genotypes
from the other parent.
 Draw your Punnett Square Here!
b. Write the gamete genotypes for one parent
at the left end of each row and for the other
parent at the top of each column.
c. Bring the gametes for each column and row
together in the boxes. These are all of the
possible genotypes for offspring created by
these two parents.
For heterozygous
combinations, always list the dominant
allele first.
d. Write the phenotype in each box as well.
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
Make a list of all of the genotypes that showed up in the offspring (fill out the table
below). If a genotype showed up more than once, list the total boxes that contained that
genotype. You may not need all the boxes provided.
Offspring
Genotype

Number of Boxes in
Punnett Square
Make a list of all of
the
phenotypes
that
showed up and the number of boxes that had each phenotype. You may not need all the
boxes provided.
Offspring
Phenotype
Number of Boxes in
Punnett Square
The next step is to determine the probability of seeing each genotype and phenotype.
Probability can be displayed in three different ways:
a. The fraction of offspring expected to have particular genotype or phenotype is
determined by placing the number of boxes with that that have each genotype on the
top (the numerator) and the total number of boxes on the bottom (the denominator).
b. The percent of offspring is determined by dividing the number of boxes with a particular
genotype or phenotype by the total number of boxes and multiplying by 100.
c. A ratio is determined by listing the number of boxes for of each genotype/phenotype in
a line and separating the numbers with a colon. The numbers in the ratio should add up
to the total number of boxes in your Punnett square.
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

Calculate the fraction and percent of each genotype produced by this cross.
Determine the genotypic ratio for this cross.
Genotype
Fraction
Percent
Genotypic
Ratio:


Calculate the fraction and percent of each genotype produced by this cross.
Determine the genotypic ratio for this cross.
Phenotype Fraction
Phenotypic
Ratio:
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Step 4:Answer the question being asked.

What is the actual question being asked?
Look back through your work. Most likely, the answer is in the work you did.

What is the answer to problem A? Write your answer in a complete sentence.
Problem B. Cystic fibrosis is a common recessive disorder. What is the
probability that two normal parents, both of whom are heterozygous for cystic
fibrosis, will have an affected child?
Step 1: Make a list of all of the information you have been specifically given in this problem.
Step 2: List anything more you can deduce from the information given.
Step 3:Use the information you’ve pulled from the problem (step 1) and what you have been
able to infer (step 2) to set up the cross.
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Step 4:Answer the question being asked.
Problem C. Huntington’s disease results from the presence of a dominant
allele and the disease does not show up until middle age (40's).
a) Could two unaffected parents in their 20’s have children with Huntington’s?
Why or why not?
b) What is the likelihood of a child having Huntington’s if only one parent is
diagnosed with the disease? Can you be sure? Explain.
Try this one on your own! Obtain some scrap paper from your instructor if you
need more room!
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Problem D. In tomatoes, red fruit is dominant over yellow fruit while tall
vines are dominant over short vines. A tomato breeder has pure
(homozygous) varieties of yellow-fruited, tall plants and red-fruited, short
plants:
a) If the breeder crosses the two varieties that he has, what will be the
appearance of the F1?
b) If a breeder crosses a tomato that is heterozygous for both height
and fruit color with a tomato that is homozygous recessive for height
and heterozygous for color, what percent of the offspring should
have short vines and yellow fruit?
Don’t forget to stay organized! Follow steps 1-4 as outlined for problem
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Date due:
Name:
Pre-lab 8: Natural Selection
This lab usually takes place before evolution is covered in class. To answer these questions,
read Chapter 18 of your textbook or, check out this excellent website:
http://evolution.berkeley.edu
1. Define microevolution.
2. List the five causes of microevolution (your book says there are four, but we usually consider
the topic of section 18.7 as another cause).
3. Describe the process of natural selection?
4. What is the role of an organism’s environment in the process of natural selection?
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Name:
Lab 8: Natural Selection
By the end of this lab, you should be able to:
 Explain the process of microevolution
 Explain the process of co-evolution
 Describe the impact of environment on adaptation
 Calculate the frequencies of phenotypes and genotypes within a population
 Graph population data
Exercise I. Predator-Prey Game: In nature, phenotypic variation exists in all populations.
Due to various reasons, some phenotypes (morphs) may be able to produce more offspring
than others, and subsequently, become more prevalent in the population, a process called
Natural Selection. If the phenotypic traits are heritable, the result will be an increase in the
gene frequency of the more successful phenotypes; a process called Evolution. In this
laboratory, we will examine these concepts by conducting a predator-prey simulation.
Simulation: For our simulation, we will use pasta types to represent different prey phenotypes
of a single prey species. Various utensils will represent different predator types, also of a single
predator species. You will carry out your “hunting” in different environments (colors/patterns
of paper, carpet, lab bench). The rules for the simulation are:
1. The simulation will be based on groups of four students.
2. Every student in a group will select a single predator morph.
3. Each group will scatter 50 of four different prey types onto the lab bench in a random
manner--making 200 total prey.
4. Predators will be allowed to “feed” for a total of 30 seconds.
5. The goal of the simulation is for each predator to eat as many prey as possible within
the 30-second time period.
6. Predators may use any technique to capture prey; however, “shoveling” of prey off of
the bench top will not be allowed.
7. “Eating” shall consist of the lifting of prey from the bench top and placement of the
prey within the paper cup.
8. At the end of the feeding period, the prey left on the bench top shall constitute the
“survivors,” and they will reproduce to create the next generation of prey.
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Look at your environment and at your prey. Make a prediction as to what will happen to each
type of prey as you hunt. Which will be the easiest to “capture”? The hardest? State your
predictions in Table A. Be sure to include a name for each prey morph! You should have a
prediction written for each morph.
Table A: Predictions of the outcome of the Predator-Prey Simulation (Prey)
Type of prey
Prediction
Type 1:
Type 2:
Type 3:
Type 4:
Look at your utensils. Make a prediction as to how effective each utensil will be in catching
prey. State your predictions in Table B. Be sure to include a name for each predator type!
Table B: Predictions of the outcome of the Predator-Prey Simulation (Predator)
Type of predator
Prediction
Predator Type 1:
Predator Type 2:
Predator Type 3:
Predator Type 4:
Feeding: When you have prepared the simulation according to the rules above, your instructor
will start your feeding session. Remember, the goal is to eat as many of the prey as possible
within the 30-second time limit.
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Calculations: The first thing you need to do is count and record the total number of each type
of prey in your stomach (cup). Each member in your group should do this and write their
results down on a sheet of paper.
Prey type
Number of Prey in
YOUR stomach
Number captured by
your entire group
Number of survivors
(50-# caught by
whole group)
Type 1:
Type 2:
Type 3:
Type 4:
Total:
Now, your group will need to perform some calculations. These calculations are based upon
frequencies. A frequency is essentially a percentage. It is found by taking the number of
specific individuals and dividing that by the total population.
Let’s calculate the frequencies of the original prey population:
Prey Calculations:
Before feeding, there were 50 of each prey type; therefore, the frequency of each is 0.25 (50 of
each/200 total). Count the number of each prey morph left alive (on the bench) and calculate
the frequencies for each. Complete Table 1 (round your answer when necessary).
Table 1: Results of Predator-Prey Game After One Round
Frequency
Prey Type
# before hunting
before hunting
Total:
50
0.25
50
0.25
50
0.25
50
0.25
200
1.0
# after hunting
Frequency after
hunting
1.0
Now, we will calculate the next prey generation. To do this, we will assume that the frequency
of prey alive will represent the frequency of the prey in the next generation. Furthermore, we
will also assume that there will always be 200 total prey at the beginning of each generation.
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Complete Table 2 (round your answer when necessary):
Table 2: Determining the Numbers of Each Prey Type in the Second Round
Prey Type
Frequency after
hunting (from Table 1)
Multiply Frequency
by 200
Number in new
population
X 200
X 200
X 200
X 200
Total:
200
Build your new population Adjust the prey on the bench top to the new population by adding
or removing the appropriate numbers of prey. Don’t start hunting yet. First you need to
determine how well your predator types faired.
Predator Calculations: We will now calculate the efficiency of each predator type in capturing
prey. To do this, we will determine the frequency of prey eaten by each predator. We start
with the four predators present in equal proportions: 1:1:1:1. Divide the number of prey each
predator type ate by the total number of prey eaten by all your predators. Complete Table 3
(round your answer when necessary).
Table 3: Determining the Efficiency of Each Predator Type
Number of Prey
Predator Type
Number at Start
Consumed
Total:
1
1
1
1
4
Frequency of Eating
Prey
1.0
To determine the new predator population, we will assume that there will always be four total
predators each round, but they represent a larger population where the ratio shifts. Therefore,
multiply the frequency of prey eaten by each predator by four. Complete Table 4. Round your
answer when necessary (you can’t have half a predator!!).
Table 4: Determining the Predator Population for Round 2
Predator Type
Frequency of Eating
Prey (Table 3)
Multiply Frequency of
Eating by 4
X4
X4
X4
X4
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Number of predators
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If one of your predator types goes extinct, you will need to make some changes. Put the tool for
the predator type that went extinct away. The person that was using that tool needs to find
another tool (the one that now is represented by 2 predators). For example, if one of the
predators is a knife and another is a spoon and knife doesn’t catch any food, he can’t
reproduce. In the next generation, there will be no predator with a knife. On the other hand, if
the predator with a spoon caught lots of prey, it will reproduce and their will be two predators
with spoons in the next generation. The number of each type of predator in your new
generation is determined by your numbers in the last column of Table. 4.
Feeding & Calculations: Repeat the 30-second feeding cycle, and complete the calculations
following each feeding. Enter your raw hunting data in Table 5 (go to the end of this lab and
pull out the last page) and then complete Tables 6-9. Repeat these cycles until either two prey
types go extinct, or until you have eaten a total of five generations of prey
Table 6: Results of Predator-Prey Simulation (Generation 2)
Prey
Type
#
survivors
Frequency
after
hunting
1.0
Total:
X 200
X200
X200
X200
X200
––
Number in
new
population
200
Predator
Type
Number
of prey
consumed
Total:
Frequency
of Eating
1.0
X4
X4
X4
X4
X4
––
Number in
new
population
4
Table 7: Results of Predator-Prey Simulation (Generation 3)
Prey
Type
#
survivors
Frequency
after
hunting
1.0
Total:
X 200
Number in
new
population
Predator
Type
Number
of prey
consumed
Frequency
of Eating
X4
X200
X4
X200
X200
X200
––
X4
X4
X4
––
200
Total:
1.0
Number in
new
population
4
Table 8: Results of Predator-Prey Simulation (Generation 4)
Prey
Type
Total:
#
survivors
Frequency
after
hunting
1.0
X 200
X200
X200
X200
X200
––
Number in
new
population
200
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Predator
Type
Total:
Number
of prey
consumed
Frequency
of Eating
1.0
X4
X4
X4
X4
X4
––
Number in
new
population
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Table 9: Results of Predator-Prey Simulation (Generation 5)
Prey
Type
#
survivors
Frequency
after
hunting
1.0
Total:
Number in
new
population
X 200
X200
X200
X200
X200
––
200
Predator
Type
Number
of prey
consumed
Total:
Frequency
of Eating
X4
X4
X4
X4
X4
––
1.0
Number in
new
population
4
Drawing conclusions: You have gathered quite a bit of raw data in this lab, but what does it all
mean? We need to gather the important numbers together in order to analyze our results.
Search through the data you have collected to complete Tables 10 and 11. The frequencies of
the prey types can be taken directly from your data tables (Frequency after hunting in Tables 2,
and 6-9). To determine predator frequencies, divide the number of each type of predator in
each generation by 4.
Table 10: Collected Prey Frequencies from Predator-Prey Game
Generation
0
1
2
3
4
5
Prey Type:
.25
.25
.25
.25
Table 11: Collected Predator Frequencies from Predator-Prey Game
Generation
0
1
Predator Type:
.25
.25
.25
.25
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Analyzing your data:
1. Plot graph of prey frequency vs. generation for each prey type in your simulation.
Generation 0 will represent the initial frequencies of the prey.
2. Plot a graph of predator number vs. generation for each predator type in your simulation.
Generation 0 will represent the initial frequencies of the predators.
3. Predators and their prey are often said to “co-evolve;” that is, each one acts on the
evolution of the other. Keeping this in mind, answer the following questions:

Describe how the ending prey population differed from the initial prey population.

What was the cause of the difference noted above?

Would your results differ if you conducted the simulation in a different environment?
Explain your answer?

Different groups in your class used different environments to perform this simulation.
Talk to another groups and discuss how their results differed. Summarize your discussion
here.

Did your results support the prediction you made in Tables A and B? Why or why not?

Describe a real-life predator-prey interaction and state how it provides an example of coevolution.
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Exercise 2. Video “The Evolutionary Arms Race”: This video demonstrates how the
process of evolution is driven by the interactions of organisms. Read through these questions
before the video begins.
Questions:
1. What seems to be driving the evolution of deadly toxin of this trait in Oregon’s Rough
Skinned newts?
2. What is the price that toxin-resistant Garter snakes pay for resistance?
3. What is the only remaining predator of humans?
4. How is the active tuberculosis (TB) microbe spread?
5. How does the release of prisoners being treated for TB lead to the evolution of drug
resistant strains of the disease?
6. Why should we be concerned about multi-drug resistant TB (MDTRB) in Russia?
7. How is Cholera transmitted?
8. What water conditions caused cholera to become more toxic? What conditions caused
cholera to become less toxic?
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9. Why are modern wild cats resistant to feline immunosuppressive virus?
10. O’Brien found a mutation in humans that made them resistant to HIV infection. Why is this
mutation common in Europeans?
11. Why do leaf cutter ants cut, but not eat plants? What organism actually digests the plant
material?
12. What kind of pest is found in the leafcutter ants’ fungal gardens? How do the ants keep this
pest under control?
13. Why hasn’t the pest developed resistance to the ant’s form of pest control?
14. Based on what you’ve seen in this movie, explain why you should ALWAYS take the entire
antibiotic a doctor prescribes to you.
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Applying What You’ve Learned:

Determine the allele frequency of your class (or at least 10 of your friends; more is
better!) for each of the following traits. Both traits have only two alleles and are
controlled by a single gene.
Number of Individuals
Trait
Frequency of Allele
Displaying Allele
Attached Earlobes
Unattached Earlobes
Widow’s Peak
No Widow’s Peak

Are the frequencies of the alleles for these two genes (earlobe shape and widow’s peak)
in anyway related? Why or why not?

Attached earlobes and having a widow’s peak are the dominant alleles of these two
genes. Does the genetic dominance of these alleles have anything to do with their allele
frequency? Explain your answer.

Choose either the earlobe shape gene or the widow’s peak gene. Assuming that natural
selection is the primary force contributing to the frequency of the two alleles of that
gene, provide a hypothesis as to why the particular allele of that gene that you found to
be more frequent (above) might be more common than the other.
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Table 5: Raw hunting Data
Round 2
Prey type
# prey in
YOUR
stomach
# captured
by group
Round 3
# at start of
hunt -# caught
by group
(survivors)
# prey in
YOUR
stomach
Type 1:
Type 2:
Type 3:
Type 4:
Total:
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# captured by
group
Round 4
survivors
# prey in
YOUR
stomach
# captured by
group
Round 5
survivors
# prey in
YOUR
stomach
# captured
by group
survivors