Biology
HS Science
Unit: 04 Lesson: 03
Cell Cycle and Mitosis
Background: The cell cycle is a series of events that take place during the life of a cell. The cell cycle is
made up of two main stages: Interphase and Mitosis. Most of the cell cycle is spent in Interphase, which
consists of G1, S, and G2. Mitosis consists of nuclear and cytoplasmic division, which is carried out during
Prophase, Metaphase, Anaphase, and Telophase/Cytokinesis and is done so that multicellular organisms can
grow (add more cells) and replace/repair tissue.
Interphase: During G1 the cell is carrying out its normal metabolic activities. During S, the cell duplicates its
genetic material. The genetic material duplicates so that when the cell divides, each daughter cell contains
the same amount of genetic material as the parent cell. During G2 the cell prepares for division.
Mitosis: During Prophase the nuclear membrane breaks down and the genetic material condenses into
chromosomes, which are visible under the microscope. Centrioles migrate to opposite poles of the cell and
microtubules attach to the centrioles. During Metaphase, the duplicated chromosomes line up on the equator
of the cell. The microtubules attach to the centromere, which holds the duplicated chromosomes together.
During Anaphase, the duplicated chromosomes separate, one of each pair being pulled toward opposite
poles of the cell. During Telophase, new nuclear membranes form around the separated genetic material,
which beings to unwind, and during Cytokinesis, the cytoplasm divides. The result is two daughter cells that
look exactly like and have the exact genetic material as, the parent cell.
In this lab, you will examine plant cells in different stages of the cell cycle. You will identify the stages and
draw them as you see them under high power.
Prophase
Metaphase
Anaphase
Telophase
G1
G2
S
Materials:
Prepared slide of onion root tip
Procedures:
1. Locate and focus on the root tip using the lowest power of your microscope. Then change to high
power.
2. Use the photomicrographs below as a guide to locate and identify Interphase and each stage of
mitosis.
© 2011, TESCCC
06/16/11
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Biology
HS Science
Unit: 04 Lesson: 03
Cell Cycle and Mitosis
3. Draw Interphase and each stage of mitosis in the Data section of your lab.
4. Count the number of cells you see in Interphase. Count the number of cells you see in each stage of
mitosis. Record your data in the Data Section.
5. Return the microscope to low power, lower the stage, and turn it off.
Data:
Stage:
Stage:
© 2011, TESCCC
Stage:
Stage:
Stage:
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Biology
HS Science
Unit: 04 Lesson: 03
Cell Cycle and Mitosis
Stage of Cell Cycle
Number
Interphase
Prophase
Metaphase
Anaphase
Telophase
Figure 1. Number of Cells in Stages of the Cell Cycle
Analysis:
1. In what stage were the majority of cells? Why do you think this is the case?
2. What percent of the cells were in the different stages?
Interphase:
Prophase:
Metaphase:
Anaphase
Telophase:
© 2011, TESCCC
06/16/11
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Biology
HS Science
Unit: 04 Lesson: 03
Cell Cycle and Mitosis
3. Describe the cell in each of the different stages.
Interphase
Prophase
Metaphase
Anaphase
Telophase
4. Why is important that the genetic material be duplicated before the cell divides?
5. Why is it important that this process be highly regulated? Discuss what might happen if cells were
allowed to divide in an uncontrolled fashion.
6. Do you think cell division occurs at the same rate in skin cells as in brain cells? Explain your answer.
© 2011, TESCCC
06/16/11
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