Mitosis of the Onion Root Tip Answer Sheet

Name _____________________ Date ___________

1. 1. Why do we study the root tip to find mitosis instead of any other part of the onion plant?

We study the root tip because it is growing therefore cells are dividing rapidly. This makes it the

best part of the plant to observe various stages of mitosis.

2. Based on you data what can you infer about the relative length of time an onion root-tip cell

spends in each stage of the cell cycle? Most cells are in interphase, the stage in which they are

carrying out the functions of the cell.

3. Based on your understanding of the structure of the chromosome, why might it take longer to

complete prophase than the other phases of nuclear division? Prophase is the longest phase of

mitosis because the chromosomes have to coil up into organized bodies. (Depending on the

students' depth of understanding they may describe the organizational structure of

chromosomes such as looped domains, etc.)

4. How do you account for variability in the data collected from different lab groups? Possible

answers: Not all lab groups had the same slide so there can be variability among the growth

rates of the plants that were used to prepare the slide. The groups may have been looking at

different areas of the root.

5. If you examined cells in the Zone of Differentiation (Zone of Maturation) would you expect to

get similar results? No Why or why not? Cells in the zone of differentiation are not dividing; they

have left the cell cycle.

6. Why did we use the pie chart to graph the data? The pie chart was used because the data

represented the parts of a whole.

Extension:

1. If you wanted to use the column graph how would you have to change the data table in

Excel? You would graph only the % of time, not the number of cells, by placing the "% of Time"

column next to the "Stage" column and high-lighting them both.