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Chapter 12

BIO SCI 93 Chapter 12: Cell Cycle and Mitosis


Department
Biological Sciences
Course Code
BIO SCI 93
Professor
Justin Shaffer
Chapter
12

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Chapter 12 pages 232-239, 242-248
The three functions of cell division is reproduction, growth and development, and tissue
renewal.
Cell Cycle: the life of a cell from the time it is first formed during division of a parent cell
until its own division into two daughter cells.
Chromosomes are the structures that DNA molecules are packaged into. Chromatin is
the entire complex of DNA and proteins that is the building material of chromosomes.
Varies in degree of condensation during process of cell division
There are 46 chromosomes in human somatic (all cells but the reproductive
cells) cells, 23 from each parent
23 are in human gametes.
The two sister chromatids are identical. Centromeres are the region of chromosomal
DNA where the chromatid is attached most closely to its sister chromatid.
Mitosis is the division of genetic material in the nucleus, which follows after cytokinesis,
which is the division of the cytoplasm.
Mitotic phase (M): includes both mitosis and cytokinesis, usually the shortest part of the
cell cycle; alternates with longer stage called interphase, which is the growth period
Interphase: accounts for 90% of the cycle; growth of cell stage in which the cell produces
proteins and cytoplasmic organelles such as mitochondria and ER.
S phase: “synthesis” – duplication of the chromosomes; second part where cell
continues to grow
G1 phase: first gap” – first part of the interphase where cell grows
G2 phase: “second gap” – third part where cell grows more as it completes preparations
for cell division
Mitotic spindle: begins to form in cytoplasm during prophase; many of the events of
mitosis depends on this; structure consists of fibers made of microtubules/assoc.
proteins; other microtubules of cytoskeleton partially disassemble to provide material
used to construct the spindle.
Centrosome: where assembly of spindle microtubules starts; a subcellular region
containing material that functions throughout the cell cycle to organize the cell’s
microtubules.
Aster: radial array of short microtubules extending from each centrosome
Kinetochore: structure made up of proteins that have assembled on specific sections of
DNA at each centromere of a sister chromatid
Metaphase plate: imaginary plane midway between spindle’s two poles where the
centromeres of all duplicated chromosomes are on
G2 of interphase
Nuclear envelope encloses nucleus, which contains one or more nucleoli. Two
centrosomes formed by duplication each with two centrioles
Have been duplicated by S phase, but has not been condensed yet
Mitotic spindle not formed yet
Prophase
Chromatin fibers become more tightly coiled, condensing into discrete
chromosomes observable with a light microscope. Nucleoli disappear;
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