Name: ______Date: ______Period: _____
Cell Cycle Activity Using Photos of Onion Root Tip Cells
1. On the website you willidentify the phase of each photo of onion root tip cells. They will be:
I – InterphaseP – ProphaseM – MetaphaseA – AnaphaseT – Telophase
2. Total each and place the numbers in the table below. Then determine the % of cells in each phase (x/36).
Then determine the proportion of a pie chart what would represent the time devoted to each phase in the cell cycle. To convert the % of cells in the phase to the degrees of the circle, change the % amount to its decimal form and use it to multiply 360o. For example, if 30% of the cells are in Prophase, then its slice of the pie chart would be calculated by: 0.30 x 360o = 108o.
Finally, assuming it takes an average of 24 hours (1,440 minutes) for onion root tip cells to complete the cell cycle, calculate the amount of time cells spent in each phase of the cycle. Use the formula provided below:
Percent of Cells in Phase x 1,440 minutes = minutes cell spent in phase
Interphase / Prophase / Metaphase / Anaphase / Telophase / Total for all phases# of cells / 36 cells
% of cells / 100%
Degrees of the circle / 360o
Time of each stage / 1440 min.
3. Now you will create an Excel pie chart. First, open an Excel spread sheet. Input your data for the number (not percentage or degree) of cells in each stage. Make sure your dataresembles the information below (use your own data!).
Number of cells – My Name Mrs. Boys (Period 1)Interphase / 18
Prophase / 10
Metaphase / 2
Anaphase / 1
Telophase / 5
Next, highlight the data, click on Insert at the top of the screen, and then select Chart. Select Pie as your “Chart Type.” Do not change the “Chart sub-type.” Click Next. Do not change any of the selections on this next screen. On the following screen, make sure your title says “Number of Cells” and also has your name. In the final screen, make sure the chart location is as a new sheet (top selection). Click Finish. Show this to Mrs. Boys.
Mrs. Boys’s Signature for chart: ______
Questions – you may use your notes, textbook, results from the lab, or the website to answer the following questions.
1) In which phase of the cell cycle does a cell spend most of its time?
2) Name two examples of human cells that reproduce through mitosis quite frequently and discuss why they need to reproduce so frequently.
3) Name one type of human cell in which the cells seldom or never reproduce through mitosis.
4) Cytokinesis (division of cytoplasm) occurs differently in plant and animal cells. Describe this difference.
5) Consider what might happen if the cell cycle became abnormal. Give an example of a cancer that occurs in the human body and give 2 possible causes or risk factors for this cancer.