LEcture 23 cell cycle

LEcture 23 cell cycle - Regulation of the Cell Cycle...

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Regulation of the Cell Cycle Campbell 6th ed: pp. 224-227 7th ed: pp. 228-230 To get ahead: before next class check Fig. 13.7 (6th ed.) or Fig. 13.8 (7th ed.)
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Cells don’t always divide. Even some bacteria can stop dividing if conditions are bad. They form inert spores until conditions improve.
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Multi-celled organisms : Many cells rarely divide in adults. Non-dividing cells remain in G0 phase. G1 S G2 G0
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Cell cycle is highly regulated even in dividing cells. Experi ment : fuse a cell in M with a cell in G1
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Result: G1 cell enters M
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2nd Experiment : fuse a cell in S with a cell in G1
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Result: G1 cell enters S!
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Conclude : something in cytoplasm controls cell cycle. Cell in M or S had a signal. After fusion; cell in G1 got the signal - AT THE WRONG TIME!
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Proteins provide the signals. Hard to identify in human cells; easier in simple “model” systems (e.g. yeast). The SAME PROTEINS work in both cells!
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Checkpoints : places where cell cycle STOPS unless it gets “go-ahead” signal
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G1 S G2 M 3 major checkpoints: in G1, G2, M phases
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Gets signal No signal: cell enters G0
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most important. Called the
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LEcture 23 cell cycle - Regulation of the Cell Cycle...

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