snc2d Lab: Cell Cycle
QUESTION: How much of its time does a cell spend in each phase of the cell cycle?
BACKGROUND
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The cell cycle includes interphase and mitosis.
The time it takes for each stage of mitosis depends on the cell type and environmental conditions but may be
estimated by counting the number of cells seen in a particular stage of mitosis from a random microscopic sample.
Since you are working with a photograph of a prepared slide, you cannot time how long it takes a cell to divide.
Based on how many cells are in a particular stage you can infer how much of its lifetime is spent in each stage.
PROCEDURE
1.
2.
3.
4.
Count the total number of cells in the sample and record the total in your data table.
On the cell diagram, mark all the cells in Prophase with a P.
Count the number of cells that you see in Prophase and record. Repeat for Metaphase, Anaphase and Telophase.
All cells that are NOT in Prophase, Metaphase, Anaphase or Telophase are in Interphase. Obtain the number of
cells in interphase by subtraction.
# of cells in interphase = total number of cells – (prophase + metaphase + anaphase + telophase)
4. Calculate the % of cells in the sample that are in each phase:
% = 100 x # of cells in the stage/ total # of cells in the entire sample
(If done correctly, all the %’s should add up to 100 %)
5. Calculate the number of degrees in a circle graph for each phase by multiplying the percentage of time the cell
spends in each phase by 360 (the total number of degrees in a circle). Record your answers in the table.
(eg. If 20% of cells are in interphase, then # of degrees in pie graph for interphase = (0.20) x 360° = 72 °
SAMPLE:
snc2d Lab: Cell Cycle
name: ___________________________________________
/12 INQ
Data:
# of Cells found in: /5
total number of
cells in sample 
prophase
metaphase
anaphase
telophase
interphase
(find by
subtraction)
% of cells in
EACH stage:
number of
degrees out of
360°
Analysis
/3
1. Draw a pie chart depicting the typical cell cycle for
an onion root tip cell. Start with Interphase at the top
(at 12 o’clock).
2. include a proper title, legend and labels. Use
different colours for the different stages.
2. In which phase of the cell cycle does a cell spend most of its time? _______________________ /0.5
3. In which phase does the cell seem to spend the least time? ______________________________/0.5
4. If the onion cell takes 12 hours to complete a cell cycle, how much time does it spend in each phase (in
hours)? Show your work.
/2
prophase
metaphase
anaphase
telophase
interphase
6. If you could see 350 onion cells through a microscope, how many of them would you expect to see in
anaphase? Show your work. /1