Name:_________________________________________________ Date:____________ Hour:___________
Mitosis Lab – Onion Root Tip Cells
Background Information:
In a growing plant root, such as an onion root, the cells at the tip of the root are constantly dividing to allow the
root to grow. Because each cell divides independently of the other cells in the root, a root tip contains cells at
many different stages of the cell cycle. Because onion root tip cells grow quickly, and the cells are large, this
makes the root tip an excellent sample to study the stages of cell division. In this lab, we will look at the cells of
an onion root tip under a microscope and count the number of cells in each stage of the cell cycle. This will help us
to determine the percentage of time that a cell spends in each stage.
Purpose: Explain why we are doing this lab.
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Hypothesis: Using what you know about the cell cycle and the diagram to the
right, predict which stages of the cell cycle onion root tip cells will spend the
least and the most time in. Choose from interphase, prophase, metaphase,
anaphase, and telophase.
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Procedure:
1. Place the slide on the microscope stage with the onion root tip pointing away from you like an arrow. Use
the scanning objective (red) to focus on the root tip. Then switch to the low power objective (yellow),
focus, and transition to the high power objective lens (blue). When you are on the high power objective
lens, focus using the fine adjustment knob only.
2. You should now be able to see anion root tip cells in various stages of mitosis.
3. Observe the box-like cells that are arranged in rows. Select a cell whose “spaghetti-like” chromosomes are
visible.
4. Sketch the cell that you selected in the box on the right.
5. Sketch three other cells in the boxes below whose internal
appearances are different from each other and the first one
that you drew in step #4.
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Name:_________________________________________________ Date:____________ Hour:___________
6. Finally, have one partner look at the cells under the microscope. This person should say the stage that each
onion root tip cell is in out-loud row-by-row. The second partner should keep a tallied list of these stages in
the data table on page #3. Use the guide below to help you identify the stages.
Interphase
Chromosomes not visible,
Nucleolus visible
Anaphase
Spindle fibers begin
to pull chromatids to
opposite sides of the cell
Prophase
Prophase
Chromosomes coiling,
Nucleolus disappearing
Chromosomes visible,
Nucleolus not visible
Anaphase
Telophase
Chromatids are pulled
to opposite sides of the
cell
Nuclear membrane
reforms, and
chromatids reach
the poles of the cell
Metaphase
Chromosomes lining up in
the middle of the cell
Telophase
Nuclear membrane reforms,
nucleoli reappear,
chromosomes uncoil,
two new cells are visible
Data:
Phase:
Tally Marks:
# of Cells:
(This is the number of
tally marks.)
Interphase
Prophase
Metaphase
Anaphase
Telophase
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Name:_________________________________________________ Date:____________ Hour:___________
Results: In the box below, create a bar graph that represents the data that you collected in the table above.
Remember to properly label your bar graph with a descriptive title, axis labels and units, etc.
Follow-Up Question: State whether your data supports (NOT proves) or refutes your original hypothesis. Provide
specific numerical data from the chart/graph to support your statement.
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