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Cell division
Mitosis
“multiply and divide”
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Figure typifies what students learn
Mitosis (so different from meiosis!)
Chromosome = colored body.
Most of what cells do is when they are
NOT dividing! -•  Introduce cell cycle
cell-cycle - Understand:
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2n is diploid,
prophase, metaphase, anaphase.
interphase is when the cell actually functions unwound chromatin vs. condensed
chromosomes
cell cycle:interphase G1, S, G2, mitosis
G = gap, S = synthesis
arrest in G1 if postmitotic
these are the cells which age
Some cells do not divide
•  brain (CNS Neurons) and heart
(myocardial cells) - do not divide,
•  why stroke and heart attack are so
damaging (no new cells replaced by
mitosis)
•  vs. in intestines, cells are constantly
replaced by mitoses from stem cells
•  in that milieu, cells digest themselves.
Information
•  homologues do not line up (contrast with
meiosis, next lecture),
•  DNA had already doubled (S=synthesis)
•  Terms to know
•  prophase, centrioles, spindle
•  Centromere (on chromosome) = kinetochore
(where microtubules attach)
•  later (metaphase) chromosomes line up at
metaphase plate
Information
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centromeres divide
anaphase, chromosomes separate
telophase when cells separate
followed by cytokinesis.
Cell division in eukaryotes to make
genetically identical daughter cells
•  FUNDAMENTAL: multicellular, all cells
have same genes (except germ cells)
Human chromosomes
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observe at metaphase block w colchicine
(they are duplicated - sister chromatids.)
Karyotype
different centromere location, size, & bands
46 chromosomes (23 pairs [diploid, 2n])
one from father and one from mother
22 pairs of autosomes & 2 sex chromosomes,
XX female, XY male
•  there are two homologues in a pair
cell cycle is controlled
•  Very specific molecules control
progress through cell cycle.
•  Many of the signal transduction
cascades control this cell cycle.
•  When things go wrong with these
controls, cancer occurs.