Onion Root Tip Mitosis

 

The purpose of this lab is to practice identifying cells in different stages of mitosis and to calculate the average number of cells that are in mitosis in an onion root tip.  This lab will be done on-line at:

 

www.biology.arizona.edu/cell_bio/activities/cell_cycle/cell_cycle.html

 

1. Start by going to the above web address and reading the first page of information.

 

2. Answer the following questions:

 

a. This lab uses onion root tip cells to study mitosis.  Why are onion root tip cells used opposed to cells from another part of the onion?

 

 

 

 

 

b. The images of cells that you will see are real.  How were the root tip cells prepared?  How were they placed on the web page?

 

 

 

 

 

3. Go to the NEXT page

 

4. The second page discuses the different stages of mitosis.  We have discussed mitosis in class but in order to successfully complete this lab you will need to review this material.  Read this page and do the following activity

 

5. On the next page of your lab book, draw the five stages of mitosis and under each drawing briefly describe what is happening in each stage.  Be sure to label each drawing.

 

 

 

 

 

 

 

 

 

DO NOT PAST HIS PAGE INTO YOUR LAB BOOK. LEAVE A PAGE BLANK TO ANSWER #5

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

6. Go to the NEXT page.  This page presents you with a

chart you will be filling in.  This is the chart:

 

 

Interphase

Prophase

Metaphase

Anaphase

Telophase

Total

Running Total

 

 

 

 

 

 

Number of Cells

 

 

 

 

 

 

  36

% of Cells in Stage

 

 

 

 

 

 

100%

 

 

 

7. Go to the NEXT page.  You will be presented with a

picture of a cell.  Decide what stage the cell was in and

click the appropriate term.  The computer will tell you

if your answer is correct.  Look back at your drawings

for help.  In the ÔRunning TotalÕ row of the data table,

keep track of the number of cells in each stage.  For

instance if the first cell is telophase, put a mark in the

telophase column.  After you have categorized all 36

cells, find the total number of cells in each stage by

counting your marks and putting the totals in the

 ÔNumber of CellsÕ row.

 

 

Analysis

 

1. Find the percent of cells in each phase.  Include this information in the chart

 

2. What phase had the most cells?  Why do you think this is so?

 

 

 

 

 

 

 

 

 

 

3. How do you think the results of this experiment would have been different if cells from onion stem had been used instead?