Laboratory
16
Mitosis and Meiosis
(LM pages 215–230)
Time Estimate for Entire Lab: 2.25 hours
Seventh Edition Changes
This was lab 15 in the previous edition. This lab was revised and now is more human-oriented than in the
previous edition.
New or revised figures: 16.3 Interphase and mitosis; 16.6 Spermatogenesis and oogenesis; 16.9 Meiosis in
humans; 16.11 Comparison of meiosis and mitosis
MATERIALS AND PREPARATIONS1
16.1 The Cell Cycle (LM pages 216-220)
Mitosis Models (LM pages 220)
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mitosis models, animal (Carolina 56-1620, -1623, -1624)
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microscopes, compound light
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slide, prepared: whitefish blastula (Carolina 30-8946)
16.2 Gametogenesis (LM pages 221-223)
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gametogenesis model (oogenesis is included in Human Development Set, Carolina
56-3124)
_____
slide, prepared: testis (Carolina 31-6428, -6434, -6446)
_____
slide, prepared: human ovary (Carolina 31-6024)
_____
microscopes, compound light
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lens paper
16.3 Meiosis in Humans (LM pages 223-227)
Building Chromosomes to Simulate Meiosis (LM page 00)
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Chromosome Simulation Biokit® (Carolina 17-1100)
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scissors
EXERCISE QUESTIONS
16.1 The Cell Cycle (LM pages 216-220)
Mitosis in Humans (LM pages 217)
Label the sister chromatids and the centromere in the drawing of a duplicated chromosome in
Figure 16.2b. 1. centromere; 2. sister chromatids
1 Note: “Materials and Preparations” instructions are grouped by exercise. Some materials may be used in more than one exercise.
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Mitosis Phases (LM page 218)
Prophase (LM page 218)
What is the chromosome number for the cells in Figure 16.3? four
Observation: Mitosis in Humans (LM page 220)
Summary of Mitosis (LM page 220)
The nucleus in the parental cell has the diploid (2n) number of chromosomes, and the nuclei in the
daughter cells have the diploid (2n) number of chromosomes. Mitosis is cell division in which the
chromosome number remains the same in the daughter cells as it was in the parental cell.
16.2 Gametogenesis (LM pages 221-223)
Slide of Ovary (LM page 223)
4. How many secondary follicles can you find on your slide? Answer will vary depending on slide. How
many vesicular follicles can you find? Answer will vary depending on slide. How does this number
compare with the number of sperm cells seen in the testis cross section? Many more sperm than
follicles are seen.
16.3 Meiosis in Humans (LM pages 223-227)
Phases of Meiosis (LM page 225)
2. Next to each cell on Figure 16.9, write 2n or n as appropriate. During meiosis I, the cells are diploid
(2n); during meiosis II, the cells are haploid (n).
Experimental Procedure: Meiosis (LM page 225)
Prophase I (LM page 226)
3. Why are these sometimes called tetrads? The homologous pair contains four chromatids.
4. Why use nonsister chromatids and not sister chromatids? Nonsister chromatids have different genetic
material. Sister chromatids have the same genetic material. If sister chromatids were involved in crossing-over,
there would be no exchange of different genetic material.
Telophase I (LM page 226)
1. What combinations of chromosomes are at the poles?
Pole A:
red-long and blue-short
Pole B:
blue-long and red-short
2. What other combinations would have been possible?
Pole A:
red-long and red-short
Pole B:
blue-long and blue-short
Conclusions (LM page 226)
• Do the chromosomes inherited from the mother have to remain together following
meiosis I? no
• Do the chromosomes inherited from the father have to remain together following meiosis I? no
• Name two ways that meiosis contributes to genetic recombination. a. crossing-over; b. independent
assortment of homologous chromosomes
Interkinesis (LM page 227)
Does DNA replication occur during interkinesis? no Explain. Chromosomes are already duplicated.
Metaphase II (LM page 227)
How many chromosomes are at the metaphase II equator? two
Anaphase II (LM page 227)
What does this action represent? This action represents centromeres dividing and daughter chromosomes moving
to opposite poles.
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Conclusions (LM page 227)
• Are the newly forming nuclei diploid or haploid? haploid
• How many cells would be present when meiosis II was complete? four
• How many chromosomes are in the parental cell undergoing meiosis II? two
How many chromosomes are in the daughter cell? two Explain. When the chromatids of the
chromosomes in the parental cell separate, they become daughter chromosomes, which segregate into the daughter cells.
Summary of Meiosis (LM page 227)
To summarize meiosis: The parental cell has the diploid (2n) number of chromosomes, and the
daughter cells have the haploid (n) number of chromosomes. Meiosis is cell division in which the
chromosome number has been reduced by half.
Fertilization (LM page 227)
A zygote contains the same number of chromosomes as the parent, but are these the exact same chromosomes? no What is another way that sexual reproduction results in genetic recombination?
During fertilization, union of gametes recombines the genes.
16.4 Mitosis Versus Meiosis (LM pages 228-229)
General Differences (LM page 228)
Table 16.2 Differences Between Mitosis and Meiosis
Mitosis
Meiosis
1. Number of divisions
One
Two
2. Chromosome number in daughter cells
Diploid
Haploid
3. Number of daughter cells
Two
Four
Specific Differences (LM page 228)
Table 16.3 Mitosis Compared to Meiosis I
Mitosis
Meiosis I:
Prophase: No pairing of chromosomes
Prophase I: Pairing of homologous chromosomes
Metaphase: Duplicated chromosomes at equator
Metaphase I: Duplicated homologous pairs of chromosomes at
equator
Anaphase: Sister chromatids separate
Anaphase I: Homologous pairs separate
Telophase: Chromosomes have one chromatid
Telophase I: Chromosomes have two chromatids
Table 16.4 Mitosis Compared to Meiosis II
Mitosis
Meiosis II:
Prophase: No pairing of chromosomes
Prophase II: No pairing of chromosomes
Metaphase: Duplicated chromosomes at equator
Metaphase II: Duplicated chromosomes at equator
Anaphase: Sister chromatids separate
Anaphase II: Sister chromatids separate
Telophase: Two diploid daughter cells
Telophase II: Four haploid daughter cells
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LABORATORY REVIEW 16 (LM page 230)
1.
2.
3.
4.
5.
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7.
8.
9.
10.
11.
12.
13.
14.
During what stage of the cell cycle does DNA replication occur? interphase
Name the stage of cell division when separation of chromosomes occurs. anaphase
By what process does the cytoplasm of a human cell separate? furrowing
Name the phase of cell division when duplicated chromosomes first appear. prophase
Where in humans would you expect to find meiosis taking place? sex organs
If there are 13 pairs of homologous chromosomes in a primary spermatocyte, how many chromosomes are there in a sperm? 13
What term refers to the production of an egg? oogenesis
Name the process that produces polar bodies. oogenesis
If members of a homologous chromosome pair are separating, what phase is this? anaphase I
If the parent cell has 24 chromosomes, how many does each daughter cell have at the completion
of meiosis? 12
What do you call chromosomes that look alike and carry genes for the same traits? homologous
Name the type of cell division during which homologous chromosomes pair. meiosis
Name the type of cell division described by 2n → 2n. mitosis
Does metaphase of mitosis, meiosis I, or meiosis II have the haploid number of chromosomes at
the equator? meiosis II
Thought Questions
15. A student is simulating meiosis I with homologous chromosomes that are red-long and yellowlong. Why would you not expect to find both red-long and yellow-long in one resulting daughter
cell? The members of a homologous pair separate during meiosis I.
16. With reference to the same homologous pair of chromosomes, describe the appearance of two
nonsister chromatids following crossing-over. Each has both red beads and yellow beads.