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I. Introduction
A. Why Do Cells Make Copies of Themselves?
1. For Growth, Differentiation, and Repair
a. "Mitosis"
2. For Reproduction
a. Binary Fission
b. "Mitosis"
c. "Meiosis"
II. Reproduction of Cells in Prokaryotes
A. Binary Fission
III. Reproduction of Cells in Eukaryotes
A. Chromosome Structure
1. Chromatin
2. Chromosomes
3. Metaphase Chromosomes
a. Chromatids [Sister Chromatids]
i. Genes
b. Centromere
c. Kinetochore
B. Chromosome Number
1. Gametes [Sex Cells] in humans have
23 chromosomes (i. e., the haploid
number [N] is 23; this is one set of
chromosomes)
2. Somatic Cells [Body Cells] in
humans have 46 chromosomes
(i. e., the diploid number [2N] is 46;
this is two sets of chromosomes)
3. Chromosome Sets (in Humans)
a. Each single set (haploid)
= 23 chromosomes:
22 autosomes
1 sex chromosome (X or Y)
b. Each double set (diploid)
= 46 chromosomes:
23 pairs of homologous
chromosomes
NOTE: In the example for mitosis given here, the diploid number of chromosomes
is assumed to be 1 (which never happens) so that what happens to individual
chromosomes will be easier to follow.
IV. The Cell Cycle
A. Overview
1. The cell cycle is a series of events
leading to cell growth and division.
B. The Mitotic Cell Cycle
1. The function of the mitotic cell cycle is to
produce two cells which are genetically
identical to the original cell, with the same
number of chromosomes and genetic
information.
2. Major Events
a. Cell Growth and Division
b. Nuclear Division
V. Mitotic Cell Cycle Stages
A. Interphase
1. "Resting Stage"; Preparation for cell division
2. Substages
a. G1
b. S
c. G2
B. Prophase
1. Preparation for mitosis
a. Nucleolus breaks down
b. Nuclear envelope breaks down
c. Chromatin forms chromosomes
d. Mitotic spindle is built
i. Spindle Fibers
ii. Asters
C. Metaphase
1. Chromosomes "line up" near the
center of the cell, along an imaginary
"metaphase plate."
2. How the chromosomes line up is
important.
a. Each chromosome lines up so that
its sister chromatids are on
opposite sides of the metaphase
plate.
D. Anaphase
1. Chromatids separate and become
individual chromosomes. (The
number of chromosomes in the cell
is temporarily doubled to 92. This
number will be reduced back to 46
during cytokinesis.)
E. Telophase (and Cytokinesis)
1. The processes of prophase are
reversed; each of the new cells
formed during cytokinesis returns to
its "resting state".
2. Telophase Processes
a. Mitotic spindle breaks down
b. Chromosomes become chromatin
c. Nuclear envelope reforms
d. Nucleolus reforms
3. Cytokinesis
a. Production of Daughter Cells
i. Animal Cells
a) Cleavage Furrow
ii. Plant Cells
a) Cell Plate
VI. Review
VII. Mitotic Cell Cycle Significance
A. Because each chromosome is duplicated
before division occurs, each daughter
cell ends up with the same number of
chromosomes as the original cell.
B. Each daughter cell is identical to the
original cell.
VIII. Summary
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Page obtained from link at URL: http://www.ric.edu/faculty/jmontvilo/109.htm
Prepared by Jerome A. Montvilo, Ph.D. for the use of his students.
Copyright © by Jerome A. Montvilo. All rights reserved.
Please send questions, comments, or suggestions to jmontvilo@ric.edu.
Last updated 15 January, 2008
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