Coyne American Institute Chromosomes Lab Experiment

Questions

1.What are chromosomes made of?

2. Research the differences that exist between mitosis and binary fission. Identify at least one difference, and explain why it is significant.

3. 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, you will look at the different stage of mitosis in an onion cell.
Remember that mitosis only occupies one to two hours of the cell cycle, whereas
interphase can take anywhere from 18 – 24 hours. Using this information and the
data from your experiment, you can estimate the percentage of cells in each
stage of the cell cycle.
Materials
Onion (Allium) Root Tip Digital Slide Images
Procedure:
Part 1: Calculating Time Spent in Each Cell Cycle Phase
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 you think 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 your
counts in Table 2.
3. Calculate the time spent by a cell in each stage based on the 24 hour
cycle using the equation below. Record your data in Table 2:
Hours of Stage = 24 x Number of Cells in Stage
Total Number of Cells Counted
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Part 2: Identifying Stages of the Cell Cycle
1. Observe the images of the onion root tip.
2. Locate a good example of a cell in each of the following stages:
interphase, prophase, metaphase, anaphase, and telophase.
3. Draw the dividing cell in the appropriate area for each stage of the cell
cycle, exactly as it appears. Include your drawings in Table 3.
4. Label the cell cycle stage on the onion root tip image (located after the
tables).
Onion Root Tip: 100X
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Onion Root Tip: 100X
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Onion Root Tip: 100X
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Onion Root Tip: 100X
Table 1: Mitosis Predictions
Predictions:
Supporting Evidence:
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Table 2: Mitosis Data
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:
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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. In what stage were most of the onion root tip cells? Based on what you
know about cell cycle division, what does this imply about the life span of
a cell?
3. Were there any stages of the cell cycle that you did not observe? How can
you explain this using evidence from the cell cycle?
4. As a cell grows, what happens to its surface area to volume ratio? (Hint:
Think of a balloon being blown up). How does this ratio change with
respect to cell division?
5. What is the function of mitosis in a cell that is about to divide?
6. What would happen if mitosis were uncontrolled?
7. How accurate were your time prediction for each stage of the cell cycle?
8. Discuss one observation that you found interesting while looking at the
onion root tip cells.
©eScience Labs, 2016