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8 Cards in this Set
- Front
- Back
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Describe interphase
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G1 - Biosynthetic activities high
S - DNA replication and centrosome replication G2 - Cell grows and checks everything is ready for mitosis |
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What are 3 types of cells that divide at different rates/if at all?
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Labile cell - multiplies continually throughout life
Stable cell - can multiply when required Permanent cell - incapable of multiplication in adult |
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Where are the checkpoints in the cell cycle?
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After G1 and before S - is environment favourable for DNA synthesis?
After G2 and before M - is all DNA replicated, DNA damage repaired? During mitosis - are chromosomes attached to mitotic spindle? |
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Cyclins and cyclin dependent kinases
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Cyclin has no enzymatic activity, CDK has to bind to cyclin to be activity
They phosphorylate target proteins which triggers a transition step in the cell cycle Mitogens activate formation of cyclin-CDK complexes |
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What is the role of the retinoblastoma protein in the cell cycle?
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When mitogens are absent, Rb protein is dephosphorylated (activated) and keeps transcription factors inactive
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What occurs to Rb protein when mitogens are present?
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Mitogens activate cyclin/CDK complexes, which phosphorylate Rb protein (deactivate), transcription factors free to activate transcription
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What are some examples of mitogens?
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Insulin, IGF-1, growth hormone
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What are approx. 50% of cancers caused by?
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Mutation in p53 gene, p53 protein which inhibits cell cycle progression allows time for repair of damaged DNA
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