“Where a cell exists, there must have been a preexisting cell.” In this virtual lab, you will examine this very principle proposed by Rudolph Virchow in 1855. The tips of an onion cell are constantly trying to expand further into the soil in their constant search for both water and essential nutrients. The tips of these onion roots are constantly undergoing mitotic division in this effort to expand. You will analyze the tips of an onion root, in order to visually identify the stages of mitosis, as well as to reinforce the timeframe of the cell cycle.
Part 1: Procedure
1.Go to the following site: http://www.biology.arizona.edu/cell_bio/activities/cell_cycle/cell_cycle.html
2.Read page 1 and click “next” at the bottom of the page.
3.Read page 2 and click “next” at the bottom of the page.
4.Read page 3 (I copied the data table for you, it is located in #7) and click “next”.
6.A new picture will appear in the same location. Choose which phase it is and then click on that phase. Complete this task until you have identified every picture that appears. There may be multiple pictures in each phase.
7.After the last picture, count all of the cells in each individual phase, and enter your findings in the top row of the table. Then, calculate the percentage of cells in each phase, and enter those values on the bottom row of the table.
1.In which phase were most cells observed? Do you agree with your data? Explain.
2.Divide the total number of cells in mitosis by the total number of cells (use the numbers you collected in the data table) to determine the percentage of cells in your sample in mitosis. This number is called the Mitotic Index. Show your calculations below.
3.What did you learn from this lab?