Name: _________________________________
BIOL 200
Post-Unit Worksheet: Unit 7
(based on Problem Set 7.2.4)
Let’s look at an experiment that was conducted using FACS (fluorescence-activated cell
sorting) technique. Here, we examine yeast cells in a gene dosage experiment. You may
wish to review Topic 7.2 on gene dosage effects.
Experimental Set-up:
Budding yeast contains several cyclins
that act at different phases of the cell
cycle. To study the role of one of these
yeast cyclins (named Cln3) you
performed gene dosage experiments by
increasing or decreasing the dose of Cln3
genes in the cells. To determine where in
the cell cycle Cln3 cyclin acts you
exposed the cells to a fluorescent dye
that binds DNA and then sorted the
labeled cells in a flow cytometer. Here
we show the FACS data from your experiments.
To help you get started:
 Recall the function of cyclins in general. What other molecules do they interact with in
order to control progression of cells through the cell cycle?
 Review how the relative amounts of DNA per cell correlates to specific cell cycle
stages.
 Hint: for this question, you need to combine information from both increased and
decreased gene dose of Cln3 to help you figure out what role in the cell cycle Cln3
cyclin is responsible for.
Questions:
a) Describe the change in DNA amount in normal yeast cells, and in yeast cells with an
increased or decreased gene dose of Cln3.
b) The x-axes differentiate between 1 and 2 ‘relative amounts of DNA per cell’. At what
stage(s) of the cell cycle do the cells have these different amounts of DNA?
c) Based on the data what conclusion can you make about where the Cln3 cyclin acts
in the cell cycle?