bio3lec1 cell cycle
TRANSCRIPT
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Cell cycleBiology 3 Kawashima
Philippine Science High SchoolSY 2009-2010
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Roles of Cell Division
Reproduction
Growth and Development
Renewal and Repair
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What happens in cell division?
Cell growth Duplication of genetic material Fission
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90% of the cell cycle
Cell growth
DNA synthesis
Checkpoints for cell division
Interphase
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Interphase
G1
SG2
Mitotic Phase
Prophase
Metaphase
Anaphase
Telophase
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Genome
•All genetic information
Chromosome
•Condensed DNA packaging•Single DNA molecule
Chromatin
•Uncondensed state of DNA molecule
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Chromatin condenses during prophase
• Nucleoli disappear• Duplicated
chromosomes appear as sister chromatids joined at the centromere
• Microtubules begin to extend from the centrosome
• Lengthening of microtubules propel centrosomes to move away from each other
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Sister chromatids organize during prometaphase
• Nuclear envelope fragments
• Sister chromatids develop a kinetochore – a protein structure found at the centromere
• Microtubules interact with sister chromatids at their kinetochores
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Sister chromatids align at the metaphase plate during metaphase
• Metaphase plate an imaginary plane equidistant between the poles
• Centrosomes now at opposite ends of the cell
• Each chromosome has numerous kinetochore microtubules attached
• Longest stage of mitosis
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Sister chromatids separate during anaphase
• Liberated chromosomes move towards the poles through “walking” centromere region first
• Nonkinetochore microtubules lengthen elongating the cell
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Chromosomes become less condensed during telophase
• Two daughter nuclei form
• Nuclear envelop reforms, arising from the endomembrane system
• Division of one nucleus into two genetically identical nuclei – mitosis – is now complete
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Cytokenesis is the division of the cytoplasm
• Cytokenesis begins in telophase
• In animals, formation of cleavage furrow “pinches” the cell into two
• In plants, a cell plate forms to divide the cytoplasm into distinct cells
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Read on Cell Cycle Checkpoints and Cancer
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