Name:
Per:
Microscope Lab: How Long is Each Phase of Mitosis?
1. Before you begin your observations, write a hypothesis for this experiment addressing which phase of the
cell cycle you think will be the longest. Use “If…then…because” format.
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Procedure:
1. Using a microscope, locate on an onion root tip slide an area with cells undergoing the process of
mitosis. After locating the cells under low power, switch to high power.
2. Count and record in Table 1 the number of cells in each phase of the cell cycle. Use Figure 1 as a guide.
Count all cells in the field of view.
Figure 1
Interphase
Telophase
Prophase
Metaphase
Anaphase
3. Move the slide so you are looking at a new root. Repeat step 2 for a total of 3 trials.
4. Total the number of cells counted in each phase and in interphase for the three areas. Record this figure
in the column marked
"Total number of cells in each phase" of Table 1. Add the total number of cells viewed in each phase and
interphase together to get the total of all cells counted. Record this number in Table 1.
We will assume that the number of cells in a phase is an indication of the time spent in that phase during
mitosis. Time spent in a mitosis phase and in interphase can be calculated if the total time for mitosis is
known. Onion cells required 12 hours (720) minutes) to complete a cell cycle (from interphase to
interphase). The amount of time needed for a phase can be calculated using this formula:
time for a phase =
number of cells in a phase
total number of cells counted
x 720 minutes
For example: if 109 cells were counted in metaphase and 980 cells were counted then:
109 x 720 = 80 minutes
980
Using your data, calculate the time required for each phase of mitosis. Use the total of the three root areas
counted. Assume that the total time for mitosis is 720 minutes. On the next page, record number of cells
observed in Table 1. Calculate minutes per phase in Table 2.
Part 1: Microscope Observations
Table 1
Trials
Interphase
Prophase
Metaphase
Anaphase
Telophase
Root 1
Root 2
Grand total of all
cells observed↓↓
Root 3
Total cells
observed in each
phase
Interphase
To calculate
percentage:
divide the total
number of cells
observed in each
stage by the
grand total of all
cells
To calculate
minutes: multiply
the percentage by
720 min.
Total minutes per
phase
Table 2
Prophase Metaphase
Anaphase
Telophase
______
______
______
______
______
X 720
min.
X 720
min.
X 720
min.
X 720
min.
X 720
min.
Part 2 Analysis

Complete sentences required unless you are asked for data or a single word. (2 points each)
2. Which phase of the cell cycle took the longest time for completion? __________________________
3. What changes occur in the DNA, nucleus and cell during the longest phase of the cell cycle?
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4. Which phase of mitosis was the longest? __________________________________________________
5. What do you think is the reason this phase of mitosis is so long? _______________________________
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6. Was your hypothesis supported by your data? Why or why not? ________________________________
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Using the data from Table 1 and the outline below, prepare a pie graph that shows the number of minutes
that onion cells spend in each phase of mitosis. Use the "time in minutes" column in Table 1 to graph your
data. The circle is divided into 18 minute sections. If a phase it not exactly 18 minutes long, approximate the
position of the line on the graph. Begin your graph in any section. COLOR EACH PHASE OF YOUR
GRAPH WITH A DIFFERENT COLORED PENCIL. Identify each phase by coloring the key to correspond to
the color on your graph. Neatness counts. (6 points)
Figure 2
Key:
Note: Each pie slice = 18 minutes
= Interphase
= Prophase
= Metaphase
= Anaphase
= Telophase
Part 3: Comparing Mitosis of Normal and Cancerous Chicken-Stomach Cells
Table 3
Time for Mitosis of Normal and Cancerous Chicken-stomach Cells (in minutes)
Normal chicken-stomach cells
Cancerous chicken-stomach cells
Interphase Prophase Metaphase Anaphase Telophase
540
60
10
30
12
380
45
10
3
10
7. In normal chicken cells, which phase of mitosis requires the longest time for completion?____________
8. In cancerous chicken cells, which phase of mitosis requires longest time for completion? _____________
9. Compare the individual mitotic phases of the cancer cells to normal cells.
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10. What is the total time needed for a normal chicken-stomach cell to complete a cell cycle?
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11. What is the total time needed for a cancerous chicken-stomach cell to complete a cell cycle?
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12. How do cancer cells differ from normal cells in the total time required for a cell cycle?
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13. Explain the relationship between mitosis and cancer. _______________________________________
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14. At this point in time, what things do we know about regulation of the rate of mitosis?
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15. List 3 reasons mitosis occurs in healthy organisms
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__________________
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Part 4: Mitosis in Salamander Kidney Cells and Pea Root Cells
Table 4
Times needed for Mitosis (in minutes)
SalamanderKidney cells
Pea-root cells
Prophase
60
Metaphase
50
Anaphase
6
Telophase
70
Interphase
186
80
40
4
12
136
16. Which cells, salamander-kidney or pea-root, show time needed to complete mitosis most like the data
you recorded in Table 1
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17. Why might the times required to complete mitosis be similar for the organism you chose in question 15?
(Hint: What kind of organism was used in part 1?)
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