Budding Yeast Cell Cycle
Summary |
Yeast represents an ideal modeling organism to to introduce the cell cycle. Students, using microscopes,
will determine the particular stages
of mitotic development in Saccharomyces cerevisiae.
Background Information
Students should be familiar with the stages of the mitotic cycle - G1, S, G2, M
Yeast grow at room temperature dividing every 90 minutes, and cannot grow past a certain size.
When this threshold is reached, a bud forms growing in size equal to its parent, then separates and
becomes an independent daughter cell.
A sample under a microscope will show a variety of ovoid shapes - a direct reflection of the length of
time for each stage of the cell cycle.
If no bud is seen, the cell is in stage G1
If a small bud is seen, the cell is in the S phase
If the bud is large, the cell is in the M phase.
Key Concepts
• Mitosis
Objectives
• Students will observe and identify three particular stages of the cell cycle
• Students will record their observations on a data sheet.
• Students will demonstrate their understanding by drawing and labeling a complete cycle.
•
Students will communicate their results by collecting data from the entire class.
Materials
A worksheet for each student/group labeled
larger sheet for class data.
Procedure
•
No Bud
Small Bud
Large Bud
and a
1.
2.
3.
Student plate 100 micro liters of sample onto a slide.
At 40X, they count the shapes they see - either no bud, small bud or large bud.
Students should sample four quadrants of the slide, then take an average for no bud, small, bud,
and large bud.
4. Students should record their date on the classroom date sheet.
5. The Class will determine the stages of cell cycle.
Assessment
• Performance—students will graph the class data.
• Assessment - diagrams of the yeast cycle which student must label themselves.
Additional Resources
Please list any Web sites, books, publications, or other resources that would be helpful for teachers or
students preparing for this lesson.
Got time?
If you have time before your presentation, it would be helpful to provide
• National Science Education Standards: http://www.nap.edu/readingroom/books/nses/html/6a.html
• Key concepts, according to the AAAS benchmarks, which provide a framework for
K-12 expectations:http://www.project2061.org/publications/bsl/online/bolintro.htm
Approximate Time
What the Teacher Is Doing
What the Students are
Materials Needed
Doing
Preparing Yeast Media
PRE LESSON
mix 1 package with 100 ml sterilized
(30mins)
water and 10 grams of sugar - leave
overnight
approx 3 hrs before, dilute sample by
taking 10 ml of yeast media and
mixing it with 90 ml of sterilized
water. Add 1 gram of sugar.
The best results for this lab occur when
yeast are in an exponential phase of
growth.
Introduction
blow up one ballon until it pops
ask students why the ballon ballons
create three ballon examples
popped - life stays small for
Focus and Motivate no bud, small bud, large bud -
many reasons
(10 mins)
identify the stages of the
dumbbell
modles
Guding students in use of microscopes. students create slides
sample media
Development
record their date from 4
slides
Explore and
sites
microscopes
generate ideas
average their data
date sheets
(30 mins)
place their class date sheet
Correlating class date to
Students graph class data
graph paper
Closure
G1, S and M phases of the cell cycle
Summarize and
On graph - answer question
plan for further
of why one was greater than
work
the other - and what would
(20 mins)
make it change