The Edward and Bella
Lab
Mitosis in Onion Root Cells
Essential Question: Where does
mitosis occur in onion root tips? Are all
cells undergoing this process at the
same time?
Hypothesis:
After you complete the lab make a hypothesis and fill it into this space 
• Procedure:
1. Place the prepared slide on the stage of the microscope, and focus with
low power objective.
2. Scan the onion root tip for a region in which cells are in various mitotic
phases.
3. Once you have identified a region, switch to high power. Find a cell that
is in one of the mitotic phases. Draw the cell you are observing, and label
its phase. Use the handout on the lab station to make this
identification.
4. Repeat step 3. Try to find cells in each of the mitotic phases.
5. Switch back to low power. In one region of the root tip, count the
number of cells in different mitotic phases. In the same region, count the
number of cells that are not undergoing mitosis. Record these numbers.
6. Repeat step 5 for three different regions of the root tip. Show which
regions you counted. Draw a simple sketch of the root tip, and shade in
the areas you observed.
Data:
• Prepare a data table appropriate to this lab.
Remember: you are counting numbers of cells
found in various stages of mitosis. There are 5
stages of cell division. You are going to make
different rounds of observations. Do the math,
make the appropriate number of
rows/columns.
Analysis/Results:
• Answer each of the following questions:
1. Are cells undergoing mitosis in every part of the onion root tip?
2. Were all of the mitotic cells in the same phase of mitosis?
3. Is the number of cells undergoing mitosis the same in every region
of the onion root tip?
4. In which regions of the root tip were the greatest number of
mitotic cells? In which regions were the fewest mitotic cells?
5. For each of the four regions you observed, calculate the
percentage of mitotic cells compared to the total number of cells
(hint: divide your visual area into quadrants (4’s) and then count
the number of cells you see in each quadrant. Divide the number
of cells in some stage of mitosis by the total number of cells in the
quadrant and you will get the percent).
Conclusion:
• How would you explain the pattern of the
occurrence of mitosis? Why would the root
have such a pattern? Write a paragraph
stating your conclusion with your
observations.
Sample Data Table
Interphase
Quadrant 1
Quadrant 2
Quadrant 3
Quadrant 4
Prophase
Metaphase
Anaphase
Telophase