WHAT MAJOR EVENTS OCCUR DURING INTERPHASE?

29 Jul WHAT MAJOR EVENTS OCCUR DURING INTERPHASE?

Compare and contrast mitosis and meiosis.

2. What major events occur during interphase?

3. Why is it important that the primary and secondary oocytes contain the majority of the cytoplasm
leaving the polar oocytes with so little?

4. What are chromosomes made of?

5. Research the differences that exist in mitosis in plant versus animal cells.

6. Critical Thinking: Cancer is a disease related to uncontrolled cell division. Investigate two known
causes for these rapidly dividing cells and use this knowledge to invent a drug that would inhibit the
growth of cancer cells.?

Experiment 1: Observation of Mitosis in a Plant Cell
In this experiment, we will look at the different stage of mitosis in an onion cell. Remember that mitosis only
occupies one to two hours while interphase can take anywhere from 18 – 24 hours. Using this information and
your experiment data, you can estimate the percentage of cells in each stage of the cell cycle.

Materials
Onion (allium) Root Tip Digital Slide Images

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Procedure:
1. The length of the cell cycle in the onion root tip is about 24 hours. Predict how many hours of the 24
hour cell cycle each step takes. Record your predictions, along with supporting evidence, in Table 1.
2. Examine the onion root tip slide images on the following pages. There are four images, each displaying
a different field of view. Pick one of the images, and count the number of cells in each stage. Then
count the total number of cells in the image. Record the image you selected and counts in Table 2.
3. Calculate the time spent by a cell in each stage based on the 24 hour cycle:
Hours of Stage = 24 x Number of Cells in Stage
Total Number of Cells Counted
4. Locate the region just above the root cap tip.
5. Locate a good example of a cell in interphase, prophase, metaphase, anaphase, and telophase.
6. Draw the dividing cell in the appropriate area for each stage of the cell cycle. Include your drawings in Table 3.

Onion Root Tip: 400X

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Onion Root Tip: 1000X

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Onion Root Tip: 1000X

Onion Root Tip: 1000X

Table 1: Mitosis Predictions
Predictions:

Supporting Evidence:

Table 2: Mitosis Data
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Number of Cells in Each Stage

Total Number of Cells

Calculated % of Time Spent in Each Stage

Interphase:

Interphase:

Prophase:

Prophase:

Metaphase:

Metaphase:

Anaphase:

Anaphase:

Telophase:

Telophase:

Cytokinesis:

Cytokinesis:

Table 3: Stage Drawings
Cell Stage:

Drawing:

Interphase:

Prophase:

Metaphase:

Anaphase:

Telophase:

Cytokinesis:

Post-Lab Questions
1. Label the arrows in the slide image below with the appropriate stage of the cell cycle.
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2. What stage were most of the onion root tip cells in? Does this make sense?

3. As a cell grows, what happens to its surface area : volume ratio? (Hint: Think of a balloon being
blown up). How does this ratio change with respect to cell division?

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4. What is the function of mitosis in a cell that is about to divide?

5. What would happen if mitosis were uncontrolled?

6. How accurate were your time predication for each stage of the cell cycle?

7. Discuss one observation that you found interesting while looking at the onion root tip cells.

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