Unlock document.
This document is partially blurred.
Unlock all pages and 1 million more documents.
Get Access
Notes to Instructors
Chapter 12 The Cell Cycle
Chapter 13 Meiosis and Sexual Life Cycles
What is the focus of these activities?
Most students can recite what happens in each phase of mitosis and meiosis. However,
What are the particular activities designed to do?
Activity 12.1 What is mitosis?
Activity 13.1 What is meiosis?
Activity 13.2 How do mitosis and meiosis differ?
These activities are designed to give students practice in translating their knowledge of
What misconceptions or difficulties can these activities reveal?
Most students don’t have difficulty reciting what events occur in each stage of mitosis or
meiosis. If you ask them to draw what is occurring in each of these stages and give a
66 Notes to Instructors
Activity 12.1
Question 2: Some students don’t understand that mitosis and meiosis occur only in
eukaryotes. This question is meant to point out that mitosis does not occur in prokaryotes,
for example, bacteria.
Question 7: Students are often confused about how to count the number of chromosomes
Activity 13.2
Most students learn mitosis and meiosis by memorizing the stages of each in order. Few
realize that the stages were named because of similarities early microscopists saw. This
Answers
Activity 12.1 What is mitosis?
What is mitosis?
1. What is the overall purpose of mitosis?
The purpose of mitosis is to produce daughter cells that are identical to the parent
the same complement (number and kinds) of chromosomes as the parent cell.
2. In what types of organism(s) and cells does mitosis occur?
3. What type of cell division occurs in bacteria?
Bacteria undergo a type of cell division called fission. Fission involves duplication
What are the stages of mitosis?
4. The fruit fly, Drosophila melanogaster, has a total of eight chromosomes (four pairs)
in each of its somatic cells. Somatic cells are all cells of the body except those that
will divide to form the gametes (ova or sperm). Review the events that occur in the
Assume you are a microscopist viewing fruit fly cells that are undergoing mitosis.
Within each of the circles (which represent cell membranes) on the following page,
draw what you would expect to see if you were looking at a cell in the stage of
mitosis indicated. If no circle is present, draw what you would expect to see at the
given stage.
68 Activity 12.1
Activity 12.1 69
Prophase
Telophase
Cytokinesis
Prometaphase
What are the products of mitosis?
5. How many cells are produced at the end of a single mitotic division?
6. How many different kinds of cells are produced at the end of a single mitotic
division?
7. Six centromeres are observed in a prophase cell from another species of insect.
70 Activity 12.1
Copyright © 2011 Pearson Education, Inc.
Haplopappus is an annual flowering plant that grows in deserts. It is of interest because
its 2n number is only four.
a. This means that cells in the vegetative parts of the plant that are not undergoing
mitosis have how many DNA molecules in their nuclei?
division.
b. During metaphase of mitosis, how many DNA molecules would be in the nucleus?
a. How many pairs of chromosomes does this organism contain? Three pairs
b. For each stage of mitosis, indicate the number of centromeres you would expect
to find and the number of copies of chromosomes attached to each centromere.
Stage of mitosis: Number of centromeres
visible per cell
Number of chromosome
copies attached to each
centromere
12.1 Test Your Understanding
Activity 13.1 What is meiosis?
What is meiosis?
1. What is the overall purpose of meiosis?
The purpose of meiosis is to reduce the diploid chromosome number by half to the
2. In what types of organism(s) does meiosis occur?
What are the stages of meiosis?
3. The fruit fly, Drosophila melanogaster, has a total of eight chromosomes (four
pairs) in each of its somatic cells. Somatic cells are all cells of the body except those
that will divide to form the gametes (ova or sperm). Review the events that occur in
the various stages of meiosis.
Keep in mind that the stages of cell division were first recognized from an examination of
fixed slides of tissues undergoing division. On fixed slides, cells are captured or frozen at
Activity 13.1 71
72 Activity 13.1
Prophase I
Telophase I
Cytokinesis
Prometaphase I
Activity 13.1 73
Metaphase II
Anaphase II
Follow one daughter cell through meiosis II.
What are the products of meiosis?
4. Consider a single cell going through meiosis.
a. How many cells are produced at the end of meiosis?
b. How many chromosomes, and which chromosomes, does each of the daughter
cells contain?
Each daughter cell has half the number of chromosomes in the parental cell. Each
5. Six centromeres are observed in a prophase I cell from another species of insect.
74 Activity 13.1
a. How many pairs of chromosomes does this organism contain? Three pairs
b. For each stage of meiosis indicate the number of centromeres you would expect
to find and the number of copies of chromosomes attached to each centromere.
Stage of meiosis:
Number of centromeres
visible per cell
Number of chromosome
copies attached to each
centromere
Nondisjunction of sex chromosomes during human gamete formation may lead to
individuals with sex chromosome trisomy. An individual with the sex chromosome
trisomy of XXY may have resulted from nondisjunction occurring in (Circle T if true, F if
false):
T/F 1. meiosis I in the father’s sperm production
13.1 Test Your Understanding
T/F 2. meiosis II in the father’s sperm production
T/F 3. meiosis I in the mother’s egg production
T/F 4. meiosis II in the mother’s egg production
Activity 13.2 How do mitosis and meiosis differ?
Review the processes of mitosis and meiosis in Chapters 12 and 13 of Campbell Biology,
9th edition, then fill in the chart. Keep in mind that the stages of cell division were first
recognized from an examination of fixed slides of tissues undergoing division. On fixed
slides, cells are captured or frozen at particular points in the division cycle. Using these
static slides, early microscopists identified specific arrangements or patterns of
chromosomes that occurred at various stages of the cycle and gave these stages names
(interphase, prophase, and so on). Later work using time-lapse photography made it
clear that mitosis and meiosis are continuous processes. Once division begins, the
chromosomes move fluidly from one phase to the next.
1. What events occur during each phase of mitosis and meiosis?
Activity 13.2 75
Copyright © 2011 Pearson Education, Inc.
Interphase Prophase Metaphase Anaphase
Telophase and
cytokinesis
Mitosis For example:
G1—cell
Chromosomes
coil and
For example:
Duplicated
Sister
chromatids
The events of
telophase are
(continues on next page)
76 Activity 13.2
Copyright © 2011 Pearson Education, Inc.
Meiosis II There may
be a short
G phase to
prepare
the cell for
Chromosomes
coil and
condense.
Nuclear
membrane
Duplicated
chromosomes
each with two
sister
chromatids,
Sister
chromatids
move to
opposite
poles of the
The events of
telophase are
the opposite
of these in
prophase.
2. Fill in the chart to summarize the major similarities and differences in the two types
of cell division (mitosis vs. meiosis). For similarities, include the event(s) that
always happen(s) at that stage, no matter which of the cell division cycles you’re
describing.
Activity 13.2 77
Interphase Prophase Metaphase Anaphase Telophase
a. What
similarities
This phase
is identical
Chromosomes
always coil
Something
always lines
Something
always
Nuclear
membrane
b. What
differences
do you
see?
No DNA
duplication
in inter-
phase of
meiosis II.
In prophase I,
homologous
chromosomes
synapse.
In mitosis
and
metaphase II,
individual
chromosomes
In mitosis
and
anaphase II,
sister
chromatids
Chromosomes
usually don’t
uncoil during
telophase I of
meiosis.
(continues on next page)
3. How do the similarities in prophase of mitosis and meiosis compare with the
similarities in telophase of mitosis and meiosis?
4. At what stage(s) does/do most of the differences among mitosis, meiosis I, and
meiosis II occur? Why do these differences exist?
The primary differences between mitosis and meiosis occur as a result of synapsis in
78 Activity 13.2
c. If the amount of DNA in a somatic cell equals Cduring G1of interphase, then
how much DNA is present in the cell during each phase of mitosis and meiosis?
Amount of
DNA in:
Interphase Prophase Metaphase Anaphase Telophase
Meiosis II Cin G1Cin
G2
C C C C
(cytokinesis
reduces the
amount to
1/2 C)
