Chapter 12
Mitosis, Meiosis, and Life Cycles
CHAPTER OUTLINE
Chromosome number
The cell cycle
Interphase is the stage between successive cell divisions
Mitosis
Duplicated chromosomes condense and become visible during prophase
During metaphase, duplicated chromosomes line up on the midplane
Plants and People: The Autumn Crocus and Colchicine
CHAPTER OBJECTIVES
1. Distinguish between a haploid cell and a diploid cell, and define homologous chromosomes.
2. Identify the phases in the cell cycle and describe the main events of each phase.
LECTURE OUTLINE
I. How is the eukaryotic cell’s genetic information arranged?
A. What are eukaryotic chromosomes made of?
II. What is the cell cycle?
A. What are the phases of the cell cycle?
1. What occurs during M phase?
a. What is the difference between mitosis and cytokinesis?
2. What important events occur in interphase?
a. At what period during interphase does cell growth occur?
C. How is the cell cycle regulated?
III. What is the overall purpose of mitosis?
A. List the stages of mitosis.
B. What happens during prophase?
1. At what stage of mitosis do the chromosomes first become visible under the light
microscope?
2. The chromosome was duplicated during interphase. What are the chromosome
IV. What is the overall purpose of cytokinesis?
A. When does it occur in relation to the phases of mitosis?
B. How does it occur in plants?
V. What is sexual reproduction?
A. How many chromosomes do reproductive cells have compared to somatic cells?
B. What are the names of the reproductive cells?
12 – 3
B. List and describe what happens during each stage of meiosis I.
1. What is synapsis and when does it occur?
C. List and describe what happens during each stage of meiosis II.
1. What is different about the period between the two cell divisions of meiosis
and the period of time between two mitotic cell divisions (interphase)?
VII. Compare and contrast mitosis with meiosis.
A. How many cell divisions are in each?
B. Does the cell division keep the chromosome number the same?
C. Is there any variation among the daughter cells produced?
VIII. Describe alternation of generations in plants.
A. What is the sporophyte?
KEY TERMS
anaphase, p. 245
apical meristem, p. 243
cell cycle, p. 242
cell plate, p. 245
phase), p. 243
gamete, p. 246
gametophyte, p. 251
genetic recombination,
meiosis II, p. 247
meristems, p. 243
metaphase, p. 245
microtubules, p. 244
TEACHING TIPS
1. There are videos available that show time–lapse photography of a dividing cell. This
helps the students visualize the process as a continuum, rather than disjunct stages.
In any case, emphasize that the phases of mitosis and meiosis are labeled by scientists for
2. As an introduction to mitosis, show the students a series of photographs (all in the same
figure) that include all of the stages of mitosis. Be sure to include interphase and a picture
of telophase in which the cell plate is present. You might also include early and late
3. To make the processes of mitosis and meiosis more concrete, have the students model
4. Begin the discussion of sexual reproduction with an overview of the animal life cycle.
Students are familiar with it and can comprehend diploid, haploid, gamete, and zygote
more easily.
5. To help students remember gametophyte and sporophyte, emphasize that the