BiO 156 Chapter 16 Powerpoint
Transcript of BiO 156 Chapter 16 Powerpoint
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BIO 156
Chapter 16
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Chromosomes, Cell Division, and the Cell Cycle
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The Cell Cycle
The cell cycleis divided intotwo parts: Interphase Cell
division
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Interphase is divided intothree parts :
G1 , S , and G2 During G1, the cell
produces RNA, proteins,and other molecules.
During the S phase, theDNA replicates
During G2, mitochondriadivide and precursors of the spindle fibers form
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Nuclear and cytoplasmic division occur separately. Cell division follows interphase. It requires two separate but related
processes: mitosis , or nuclear division, andcytokinesis , or cytoplasmic division.
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Human body cells contain 46 chromosomes that
contain all of the genetic information required tocontrol cellular activity. Each organism has a set number of
chromosomes All body cells, except the germ cells, are called
somatic cells. Body cells contain a full complement of
chromosomes and are described as diploid. Germ cells or gametes contain half the
number of chromosomes of somatic cells and
are referred to as haploid cells.
The Chromosome
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Chromosomescondense after replication, whichfacilitates mitosis. Condensed
chromosomes aremetabolicallyinactive.
The number of chromatids inchromosomesvaries, dependingon the stage of thecell cycle.
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Amniocentesis
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Normal Karyotype
Downs Syndrome Karyotype
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Cell Division
Mitosis is divided into four stages: Prophase
Metaphase Anaphase Telophase
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Prophase Chromosomes condense Nuclear envelope disappears Centrioles divide and migrate to opposite poles
of the dividing cell Spindle fibers form and attach to chromosomes
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Prophase
ProphaseInterphase
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Metaphase Chromosomes line up on equatorial plate of
the dividing cell. Anaphase
Chromosomes begin to separate.
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Telophase Chromosomes
migrate or arepulled to oppositepoles.
New nuclear envelope forms.
Chromosomesuncoil.
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Cytokinesis, the division of the cytoplasm, ismade possible by contraction of microfilaments beneath the cell membrane. Cytokinesis begins in late anaphase or
early telophase. In human cells, cytokinesis results from the
contraction of microfilaments lying beneaththe plasma membrane.
Mitosis
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Control of the Cell Cycle Many factors appear to control the cell
cycle. Research suggests the cell cycle is
controlled in part by chemical messagesproduced in the cytoplasm.
External controls such as hormones,
growth regulators, and cell contact areimposed on the cell.
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