why do cells divide? genetically programmed cell volume gets too big external stimulus dividing...
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Why do cells divide?
Genetically Programmed
Cell volume gets too big
External Stimulus
Dividing bacteria
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Cell division = One cell makes two cells
Parent cell
DNA replicates
Two daughter cells are genetically
identical to each other and to parent
cell = clones
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Chromatin = uncondensed DNA Chromosome = condensed DNA
The same DNA can appear in two forms
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1 Chromosome 1 chromatid per chromosome
1 DNA double helix
1 Chromosome 2 chromatids per chromosome
2 DNA double helices
DNA replication
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Cell division in eukaryotic cells:
Karyokinesis = division of the nucleus
Cytokinesis = division of the cytoplasm
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Interphase 1. DNA called chromatin
2. DNA replicates
3. Cell does normal activities
4. Not a phase of mitosis
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DNA = Chromatin
Interphase nucleus
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Interphase
Chromatin in nucleus
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Mitosis
1. Prophase
2. Metaphase
3. Anaphase
4. Telophase
Know this page
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Prophase
Nuclear membrane disappears
Nucleolus disappears
Chromatin condenses into chromosomes
Spindle fibers appear
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Chromatin
Chromosomes
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MetaphaseChromosomes line up in center of cell
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Chromatids (DNA double helix)
Two chromatids per
chromosome
Centromere = holds chromatids together
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Anaphase =
Sister chromatids separate from each other
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Telophase
Cytokinesis makes 2 new cells
Chromosomes decondense into chromatin
Nucleolus reappears
Nuclear membrane reappears
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Early Telophase
Late Telophase
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Animal cell membranes
pinches together
between two new cells
Plant cell wall grows
between two new cells
Cytokinesis
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Plant Cytokinesis =
division of cytoplasm
Interphase
Telophase
AnaphaseMetaphase
Telophase
Telophase
ProphaseProphase
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http://www.unm.edu/~asmund/mitosis.jpg
Interphase
Animal cytokinesis = pinching of plasma
membrane Late Telophase
Early telophase
Anaphase
Prophase Metaphase
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http://images.google.com/imgres?imgurl=www.cll.wayne.edu/isp/mrichmon/Mitosis.gif&imgrefurl=http://www.cll.wayne.edu/isp/mrichmon/mitosis.htm&h=365&w=366&prev=/images%3Fq%3Dmitosis%26start%3D20%26svnum%3D10%26hl%3Den%26lr%3D%26ie%3DUTF-8%26oe%3DUTF-8%26sa%3DN
Plant or Animal cell
mitosis?
Plant
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Telomeres = break off and lead to cell death
and aging.Telomeres
Telomerase
Enzyme prevents loss of telomeres
Found in 95% of Cancer cells
Makes cells immortal
Cancer drug = telomerase inhibitor