Why do cells divide?

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Dividing bacteria
Why do cells divide? Genetically
Programmed Cell volume gets too big External
Stimulus
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Parent cell
Cell division One cell makes two cells
DNA replicates
Two daughter cells are genetically identical to
each other and to parent cell clones
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The same DNA can appear in two forms
Chromatin uncondensed DNA Chromosome
condensed DNA
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1 Chromosome 1 chromatid per chromosome 1 DNA
double helix
DNA replication
1 Chromosome 2 chromatids per chromosome 2 DNA
double helices
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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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Interphase nucleus
DNA Chromatin
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Interphase
Chromatin in nucleus
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• Mitosis
• Prophase
• Metaphase
• Anaphase
• Telophase

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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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Metaphase Chromosomes line up in center of cell
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Centromere holds chromatids together
Chromatids (DNA double helix)
Two chromatids per chromosome
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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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Plant cell wall grows between two new cells
Cytokinesis
Animal cell membranes pinches together between
two new cells
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Prophase
Interphase
Prophase
Telophase
Metaphase
Anaphase
Telophase
Telophase
Plant Cytokinesis division of cytoplasm
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Interphase
Prophase
Metaphase
Animal cytokinesis pinching of plasma membrane
Late Telophase
Anaphase
Early telophase
http//www.unm.edu/asmund/mitosis.jpg
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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