Download Mitosis-U of Arizona tutorial

Columbia High
School
BIoLoGY LEe
Student's Name:
Lab Day:
Teacher:
Problem: How do cells preserve their genetic information during division?
Introduction: Cells reproduce themselves by a precise method of replicating and transmitting genetic
material from the parent cell to daughter cells by means of mitotic cell division. There are five visible
stages to mitosis that you should be able to see with a light microscope.
Interphase: This is called the resting stage because no chromosomes are visible. Actually, it is during this
phase that the invisible chromosomes are replicating themselves.
Prophase: During this stage the chromosomes become visible, already doubled. The nuclear membrane
starts to disappear and a network of threadlike fibers begins to arrange itself into a spindle
shape, tapered at both ends ofthe cell.
Metaphase: Chromosomes can be seen lined up along a plane through the center of the cell called the
equator.
Anaph"ase: The double stranded chromosomes begin to separate and the individual chromatids move
toward opposite sides of the cell. At the same time, the cell membrane starts to pinch in and
the beginnings of two cells can be seen.
Telophase: The new nuclear membrane has formed and the pinching in of the cell membrane has been
completed, dividing the cell into two separate cells that are still attached. In plant cells, which
have rigid cell walls, the cell membrane cannot pinch in, but instead, a cell plate appears
between the two new nuclei and a new cell wall forms.
F:rly hophase
late Prophase
Metaphase
Anaphase
Telophase
Procedures:
1. Set your web browser to http://www.biolo=ey.arizona.edu. At the left side of the page that comes up, in
the Activities column, select "Cell Biology Onion Root Tips"
2. Read through the description of each of the phases of mitosis and answer the following questions:
L. During what stage is the cell involved in norrnal metabolic activities?
b. During what stage do chromosomes become visible.
c. What happens along the "metaphase p1ate"?
d. During what phase do the replicated chromosomes begin to separate?
e. During what phase does cytokinesis or cell partitioning appear?
3. Go on to the activity during which you will be identifying 36 cells in different stages of mitosis and
keeping a count of the number of cells in each phase. Use the table below to keep track of your count.
([he program will tell you if you are incorrect.)
Obsetvations:
Analysis:
1.
From your observations, which phase was the most coflrmon among the observed cells?
2. What does this data tell you about the amount of time a cell actually spends dividing?
3. How is mitosis important to a cell?
4. Why would you expect to find matry examples of cells undergoing cell division in a root tip and fewer
examples in the stem of the same plant?
5. Why do most biologists object to the use of the term "resting stage" to describe Interphase?
6. Use your textbook or another source and define the following terms:
a.
aster-
b. centromere
c. centriole
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7. How does the process of mitosis differ in animal and plant cells?
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