Test Review – Chromosomes, Meiosis, Science & Genetics
KEY
Please the following questions in your notebook. (except #4)
1. How many chromosomes would be in a human skin cell? 46(23 pairs) A human sperm?
23 (no pairs)
2. How would two chromosomes in a homologous pair be similar and how would they be
different? They are the same size, shape and have the same genes but one comes
from Mom and one comes from Dad and the genes may have different alleles
(slightly different recipe for the protein)
3. What is different about the chromosomes of human males and females? For the last
pair of chromosomes females have a normal homologous pair (XX), but males have
one large and one small chromosome is this pair (XY)
4. Fill in the blanks on the diagram below with the following terms -homologous pair,
sister chromatids, chromosome, super chromosome. What do the two colors
represent?
chromosome
Super chromosome
The other blank is
“homologous
pair” but I can’t
get it to label on
the blank
Sister chromatids
the two colors represent the chromosomes that came from this person’s Mom and the
chromosomes from this person’s Dad
5. How is a regular chromosome different from a “super chromosome” or “duplicated
chromosome?”A regular chromosome is one piece of DNA, but a super chromosome is
two identical copies bonded together to form an X shape. At what point in the life of a
cell do we find these super chromosomes? Super chromosomes are only found when a
cell is preparing to divide (mitosis or meiosis)
6. How many copies of each chromosomes does a person have? How many copies are
passed on in each gamete? (A person has two copies of every chromosome but only
passes one copy on to each child)
7. In meiosis how do the ending cells compare with the staring cell? (The ending cell has
half the number of chromosomes as the starting cell, and the ending cell only has
one chromosome of each pair)
8. What is the main event that happens in meiosis 1? Homologous pairs are separated
Meiosis 2 Sister chromatids are separated?
9. For each of the diagrams below determine if the cell is in meiosis 1 or meiosis 2.
Meiosis 1 (you can
tell because homo pairs
Are present)
Meiosis 2 (you can tell
because homo. pairs are not there
and sister chromatids are being pulled apart)
10. Every egg or every sperm you make will be different. Explain two things that happen in
meiosis that cause this variation. 1. The way homologous pairs line up. In meiosis 1
pairs line up together before they separate. The way they line up is random in
respect to whether the chromosome came from the mother or the father. In humans
there are over 8 million different ways the 23 pairs can line up 2. Crossing over.
When the pairs line up they sometimes switch small amounts of DNA between the
“Mom” chromosome and “Dad” chromosome.
11. What is the difference between coding and noncoding DNA? Coding DNA has recipes to
make proteins (genes). Noncoding DNA helps prevent mutations, turns genes on
and off and likely has some other functions that we don’t understand well.
12. Write two scientific and two nonscientific statements about dogs Scientific- “Dogs kill
more humans a year than car accidents” & “Dogs have 36 chromosomes.”
Unscientific – “Dogs are better than cats,” & “Dogs are magical.”
13. Is the following statement scientific or not? Explain
Driving faster than the speed limit will increase your chances of dying in a car accident.
Scientific. Scientific statements must be testable, based on physical evidence and
able to be disproven. Scientific statements may or may not be accurate, but they are
testable.
14. What is the difference between an observation and an inference? An observation is
data collected with the senses or technological extensions of the senses. An
inference is a reasonable assumption based on observations. Find a kitchen utensil
in your house and make two observations and two inferences about it.
Observation: Has a hand shaped bar Inference: operated by hand
Observation: metal tines move around and around Inference: mixes
things
15. Can a theory ever become a law? Explain. No. A theory can never
become a law. A law simply states an observation that happens all
the time. A theory explains WHY something happens. They are two
different types of statements and one cannot become the other. Can a hypothesis
become a theory? Explain Yes, a hypothesis can become a theory. Both are
explanations of why something happens. A hypothesis has little data to support it
while a theory has A LOT of data to support it. In fact a theory is the best scientific
explanation for why something happens.
16. Everyone has ____2_____ copies of each gene. When a person makes a gamete they only
pass on __1_____ copy.
17. Tongue rolling is dominant (T) to not being able to roll your tongue (t). Homer and
Marge have four children. Two can roll their tongue and two can not. Explain how this
is possible. Use a punnett square to help explain your answer.
Marge and Homer could both be heterozygous – meaning that they have one allele for
tongue rolling and one allele for not tongue rolling. If one or both of them pass on an allele
for tongue rolling then the child will be able to roll their tongue, since the rolling allele is
dominant. If both Homer and Marge pass on their non rolling allele then the child will not
be able to roll their tongue.
18. In cats being tabby (T) is dominant over being solid color (t). Two heterozygous tabby
cats mate. What is the expected genotypic and phenotypic ratios for the offspring?
19. Why are some traits inherited together and some separately
Traits determined by genes on the same chromosome will be inherited together.
When you make your gametes you will give either your Mom’s chromosome or your
Dad’s, and all the genes on that chromosome will be passed down as a package.
Traits determined by genes on different chromosomes can be passed on separately.
You don’t have to give all your Mom’s chromosomes or all your Dad’s.
20. A black cow and a white cow have a black and white spotted cow. What is this an
example of?
Codominance – both phenotypes show up in a heterozygote
21. A gene is a segment of ________DNA____________ that contains a recipe to make a
__________protein_______________. Which ______amino_________________
__________acids____________ make up the protein determine the ___________shape______________
of the protein which then determines the ________function__________________ of that protein