Download Onion cells as seen under a light microscope

Name:
Class:
Date:
# ___ Lab – The Cell Cycle in Onion Root Cells
Purpose: To identify the phases of the cell cycle.
Procedure:
1) Look at the phases of mitosis in the diagrams that follow. Note that the specimens have been stained so that
we can see the chromosomes more clearly. Use them as references to identify the phases of mitosis on the
picture of the onion root cell on page 3.
Interphase
Prophase
Sources: http://www.ndpteachers.org/perit/biology_image_gallery1.htm; http://micro.magnet.fsu.edu/micro/gallery/mitosis/mitosis.html
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Metaphase
Anaphase
Telophase
After Cytokinesis
Sources: http://www.ndpteachers.org/perit/biology_image_gallery1.htm; http://micro.magnet.fsu.edu/micro/gallery/mitosis/mitosis.html
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2) Look at the picture of onion root cells on high power. Create a data table in the Data and Observations section
below. Record the total number of cells in the picture. Record the number of cells observed in each part of the
cell cycle: interphase, mitosis (all four parts), and cytokinesis. Include a column for the percentage of cells
undergoing each part of the cell cycle. Note: It will be easier to count and keep track by following rows. (See
diagram C on p. 215 of your text for a guide for counting.)
Data and Observations:
Onion Root Cells on High Power
Data Table:
Stage of mitosis
Interphase
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis
Total number of cells
Number of
cells
Percentage in
each stage
100%
Sources: http://www.ndpteachers.org/perit/biology_image_gallery1.htm; http://micro.magnet.fsu.edu/micro/gallery/mitosis/mitosis.html
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Analyze and Conclude:
1) From the picture on page 3 of this lab sheet, what part of the cell cycle did you see most often? Why?
2) Where might you look for cells in the human body that are undergoing mitosis?
3) There are times when you will not be able to observe every phase of mitosis in a slide. Give one reason why
this might be the case.
PAGE 214 AND 215 FROM YOUR TEXT BOOK
4) Look at the diagram of the onion root tip on page 214 of your text.
A) What part of the onion is area X?
B) What part of the onion is area Y?
5) Observe Which area of the onion root tip (X or Y) had the greatest percentage of cells undergoing mitosis? The
lowest? Use specific totals from your data table to support your answer.
6) Predict If mitosis is associated with rapid growth, where do you believe is the location of most rapid root growth,
area X or Y? Explain your answer
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Sources: http://www.ndpteachers.org/perit/biology_image_gallery1.htm; http://micro.magnet.fsu.edu/micro/gallery/mitosis/mitosis.html
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7) What factors might cause misleading results? How could you avoid these problems?
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Make and use Graphs:
Prepare a circle graph that shows the total number of cells counted in area X and percentage of cells in each phase
of mitosis.
Total number of cells per phase
percentage of cells per phase
Sources: http://www.ndpteachers.org/perit/biology_image_gallery1.htm; http://micro.magnet.fsu.edu/micro/gallery/mitosis/mitosis.html
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YOUR DRAWINGS AS SEEN FROM THE MICROSCOPE (AT LEAST 8 DIAGRAMS- LABELLED)
Sources: http://www.ndpteachers.org/perit/biology_image_gallery1.htm; http://micro.magnet.fsu.edu/micro/gallery/mitosis/mitosis.html
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