Download Cell Cycle Lab File

The Cell Cycle
Objectives: 1. Identify the phases of the cell cycle
2. Determine the time a cell spends in each part of the cell cycle.
3. Understand the purpose of the cell cycle.
Procedure:
1. Examine a prepared onion root tip slide. Using the lowest power of your microscope,
find the onion root tip. Find the area just above the tip of the root. This is where the
cells are dividing most rapidly.
2. Work your way up to your microscope’s highest power, and start looking at individual
cells. Find an area with active mitotic division.
3. Working with your partner, examine each cell in your field of view, and identify the
phase of the cell cycle that each cell is in. Record in the data table the number of cells in
each of the five phases that you view.
4. Switch with your partner, and have them examine a different root tip. Record in the
data table the number of cells in each of the five phases that your partner views in this
root tip.
5. Add the number of cells in both root tips together for the phase total.
6. Calculate the fraction of cells in each phase by dividing the cells in that phase by the
total number of cells that you counted. Leave this data as a decimal.
7. Calculate the percent of time that a cell spends in each phase by multiplying your
decimal in step 6 by 100%.
8. Calculate the number of degrees in a circle graph for each phase by multiplying the
decimal in step 6 by 360 degrees.
9. Make a circle graph showing the percentage of time a cell spends in each phase of the
cell cycle. Label each portion of the circle with the phase it represents.
1. According to your results, in which phase of the cell cycle does a cell spend most of its
time? The least time?
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2. Explain how a slide of stained cells can be used to estimate how much time a living cell
spends in each phase of the cell cycle.
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3. Why is it important to have a large cell count for this activity?
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4. In what cells of a human does mitosis occur? _________________________________
5. How many cells exist by the end of the cell cycle? _____________________________
6. Name three reasons why the cell cycle is necessary?
a)
b)
c)
7. How many chromosomes are in human cells produced by mitosis? _______________
8. Why are chromosomes not visible during interphase?
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9. How do the daughter cells compare genetically to the mother cell?
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10. Explain why cell division is referred to as the cell cycle.
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Data Table 1
Phase
Number of
cells in first
root tip
Number of
cells in
second root
tip
Phase cell
total
(Root 1 + 2)
Fraction of
cells in this
phase
(Decimal
form)
Percent of
time a cell
spends in this
phase.
Number of
degrees in a
circle graph
for this
phase.
Circle Graph
Interphase
Prophase
Metaphase
Anaphase
Telophase