Name _____________________________________
Due Date __________________
Hr. _______
How Long is Each Phase of Mitosis?
Do all phases of mitosis require the same amount of time for completion? This can be answered by counting the
number of onion root-tip cells in the four phases of mitosis and in interphase. Interphase and the 4 phases of
mitosis together are called the cell cycle.
Part A- Determining the Time Required for Each Phase
Assume that the number of cells in a phase is an indication of the time spent in that phase during mitosis. Onion
cells require 12 hours (720 minutes) to complete a cell cycle (from interphase back to interphase). The amount of
time needed for a phase can be calculated using this formula:
Time for a phase =
Number of cells counted in phase
Total number of cells counted overall
Using your data, calculate the time required for each phase of mitosis.
x
720 minutes
Assume that the total time for mitosis is 720 minutes.
Data and Observations
Phase
Number Counted in
Phase
(Your Data from previous Lab)
Class Data
Number Counted in Phase
Total Time Spent in
Phase (in minutes)
% of Total Time
Spent in Each
Phase
Interphase
Prophase
Metaphase
Anaphase
Telophase
Total # of Cells Overall:
Total time:
Analysis of Results
1. Using the class data and your calculations, which phase of the cell cycle takes the longest time for completion?
2. What is the next longest phase?
3. Which phase takes the shortest amount of time?
4. Again using the class data make a pie graph that shows the number of minutes that onion cells spend in each
phase of the cell cycle. Color each phase with a different color and make a key/label it.
5. Table 2 shows average times required for normal and diseased chicken-stomach cells to complete mitosis.
a. In normal chicken cells, which phase requires the longest time for completion? ___________________
b. How do your personal results compare with the times shown in Table 2? Are they similar?
Table 2 – Time for Mitosis of Normal & Cancerous Chicken-Stomach Cells (in minutes)
Interphase
Prophase
Metaphase
Anaphase
Telophase
Normal chicken- stomach cells
540
60
10
3
12
Cancerous chicken- stomach cells
380
45
10
3
10
6. What is the total time needed for a normal chicken-stomach cell to complete a cycle? __________________
7. What is the total time needed for cancerous chicken-stomach cells to complete a cycle? _________________
8. How do cancer cells differ from normal cells in the time spent for each phase?
9. What do you think is the outcome of this change? What is happening overall to these cancerous cells?
10. What might have been the cause of the chicken cells becoming cancerous?