NAME:_____________________________DATE:______________HR:______________
Time for the Cell Cycle
Question: Do all the phases of the cell cycle require the same amount of time for completion?
Hypothesis: _________________________________________________________________________
To testy our hypothesis you will be completing an experiment using the data from onion root tip cells.
Many cells in one specific phase indicate that a long period of time is required for the completion of that
phase. Few cells in a specific phase indicate a short period of time is required for completion of that
phase.
Materials:
1. Lab Directions
2. Data Recording Sheet
3. Onion Root Tip Diagram
4. Pie Chart Graph Paper
Procedure
1. Count and record in Table 16-1 the number of cells in each phase of the cell cycle.
a. Count all cells in the field of view and use Figure 16-1 as a guide.
2. Total the number of cells on the onion root sample diagram and ensure that this equals the
number of cells you counted and record this number in “total number counted.”
3. Once the number of cells column is complete move on to the math to determine time in each
stage column.
4. To calculate the time in each stage use the following formula:
Time for a Phase (min)=(# of cells in a phase/Total #of cells counted) X total time to complete cell cycle
Important!! The total time to complete the cell cycle is 720 minutes in an onion root tip cell
So your formula for this type of cell and this experiment is:
Time for a Phase (min)=(# of cells in a phase/Total #of cells counted) X total time to complete cell cycle
5. Using your data from Table 16-1 and the outline below, prepare a circle graph which shows the
number of minutes that onion root tip cells spend in each phase of the cell cycle.
a. Graph your data using the “Time in Minutes” column from Table 16-1
b. The circle is divided in to 18 minute sections. Each section of the graph equals 18
minutes. If a phase is not exactly 18 minutes or a multiple of 18 approximate the
position of the line on the graph.
c. Shade each phase of your graph with colored pencils and label your key accordingly.
d. Label where G1, S, and G2 would occur.
e. Outline and label the phases that are a part of Mitosis in black marker or color pencil
and label this area “Mitosis.”
6. Using the graph you completed answer the questions that follow.
NAME:_____________________________DATE:______________HR:______________
Phase of the Cell Cycle
Number of
Cells
Data Table 16-1
Math to Determine the time in
Each Stage
Time (in Minutes) In
Each Stage
47
XXXXXXXXXXXXXXXXXXXXXXXXXX
XXXXXXXXXXXXXXXXXXXXXXXXXXXX
XXXXXXXXXXXXXX
XXXXXXXXXXXXXXX
Interphase
Prophase
Metaphase
Anaphase
Telophase
Total Number of Cells
Counted
Graph 16-1
Title:___________________________________________
NAME:_____________________________DATE:______________HR:______________
Analysis Questions:
1. Which phase requires the longest time for completion?
2. Which phase requires the shortest time for completion?
3. What phase is not accounted for in your graph? Why do you think this is so?
4. Using what you have learned in this activity read the table below to answer the questions that follow.
Phase of the Cell
Cycle
Interphase
Prophase
Metaphase
Anaphase
Telophase
Table 16-2
Time (Minutes) It takes Normal
Chicken Cells to Complete Each Stage
540
60
10
3
12
Time (Minutes) It takes Cancerous
Chicken Cells to Complete Each Stage
380
45
10
3
10
a. What is the total time needed for a normal chicken stomach cell to complete the cell cycle?
b. What is the total time needed for a cancerous chicken cell to complete the cell cycle?
c. How do cancer cells differ from normal cells in time required for mitosis?