Lecture 4 - Mitosis
I. There are two general types of cells – somatic and germ cells
A. somatic cells
B. germ cells
C. chromosomes often come in “pairs”, called homologues
1.
2.
3.
4.
D. cells of given species have characteristic number of sets of chromosomes
- eg. Humans have 23 pairs, or 46 chromosomes
1. diploid (2n)
- somatic cells of diploid organism are generally diploid
2. haploid (1n)
- germ cells of diploid organism are haploid
II. Two types of cell division
A. mitosis – produces same ploidy as mother cell eg. 2n
B. meiosis – produces half ploidy of mother
cell eg. 2n
4 X 1n
2 X 2n
interphase
S
III. Mitotic cell cycle
G1
G2
mitosis
- a brief comparison of mitosis vs. meiosis
mitosis
M
meiosis
- two progeny with same
ploidy as parent cell
- four progeny with half the
ploidy of parent cell
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IV. Importance of mitosis
A. mitosis – precise process of nuclear division that ensures that each daughter receives
a chromosome complement identical to the parent cell
V. Overview of mitosis (each chromosome present as duplicated structure)
A. chromosomes condense and align.
B. chromosomes divide longitudinally.
C. separated halves move to opposite
poles.
D. cell usually divides
VI. Steps of mitosis – greater detail
- interphase (G1, S and G2 phases)
- cell not going through mitosis
- chromosomes are not condenses
- DNA replicated during S phase
A. prophase (eg. diploid cell with two
of chromosomes)
pairs
1.
2.
B. metaphase
2
C. anaphase
D. telophase
VII. Mitotic cell cycle, one more time with emphasis on DNA
(Note: In interphase the chromosomes are not condensed.)
interphase
S
G1
G2
mitosis
M
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