Why do cells divide? Genetically Programmed Cell volume gets too big External Stimulus Dividing...
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Transcript of Why do cells divide? Genetically Programmed Cell volume gets too big External Stimulus Dividing...
Why do cells divide?
Genetically Programmed
Cell volume gets too big
External Stimulus
Dividing bacteria
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
Chromatin = uncondensed DNA Chromosome = condensed DNA
The same DNA can appear in two forms
1 Chromosome 1 chromatid per chromosome
1 DNA double helix
1 Chromosome 2 chromatids per chromosome
2 DNA double helices
DNA replication
Cell division in eukaryotic cells:
Karyokinesis = division of the nucleus
Cytokinesis = division of the cytoplasm
Interphase 1. DNA called chromatin
2. DNA replicates
3. Cell does normal activities
4. Not a phase of mitosis
DNA = Chromatin
Interphase nucleus
Interphase
Chromatin in nucleus
Mitosis
1. Prophase
2. Metaphase
3. Anaphase
4. Telophase
Know this page
Prophase
Nuclear membrane disappears
Nucleolus disappears
Chromatin condenses into chromosomes
Spindle fibers appear
Chromatin
Chromosomes
MetaphaseChromosomes line up in center of cell
Chromatids (DNA double helix)
Two chromatids per
chromosome
Centromere = holds chromatids together
Anaphase =
Sister chromatids separate from each other
Telophase
Cytokinesis makes 2 new cells
Chromosomes decondense into chromatin
Nucleolus reappears
Nuclear membrane reappears
Early Telophase
Late Telophase
Animal cell membranes
pinches together
between two new cells
Plant cell wall grows
between two new cells
Cytokinesis
Plant Cytokinesis =
division of cytoplasm
Interphase
Telophase
AnaphaseMetaphase
Telophase
Telophase
ProphaseProphase
http://www.unm.edu/~asmund/mitosis.jpg
Interphase
Animal cytokinesis = pinching of plasma
membrane Late Telophase
Early telophase
Anaphase
Prophase Metaphase
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
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