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Lecture 30 - Lecture 30 Monday The mitotic cyclin B1...

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Lecture 30. Monday (4-11-11)
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The mitotic cyclin B1 accumulates in the nucleus in the start of mitosis 1. Cyclin B1 was labeled with a green fluorescent protein and injected into a HeLa cell that was in G2 phase. It is seen in the cytoplasm but not as much in the nucleus 2. When the cell begins mitosis, the cyclin B1 accumulates in the nucleus
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Cell Cycle Checkpoints
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Figure 18-13 Essential Cell Biology (© Garland Science 2010) CdK inhibitor proteins can act as “molecular brakes” to stop the cell cycle from progressing to the next step Cell cycle arrest No, COPs are not needed for all cell arrests 1. “Sensors” detect DNA damage or cellular abnormalities 2. The cell cycle is arrested, stalling progression to the next step 3. During this delay, DNA damage is repaired or the cell defect is corrected
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Figure 18-3 Essential Cell Biology (© Garland Science 2010) Three main checkpoints: 1. G1 checkpoint 2. G2 checkpoint 3. Mitosis checkpoint What happens if the checkpoint isn’t working well?
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CDK (kinase) Cyclin (regulator) CDK (kinase) Cyclin (regulator) p27 p27 is a CdK inhibitor. It must be removed before the cell can move into S phase. An example of a checkpoint protein What would happen if a cell was missing p27?
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The brown mouse is a p27 knockout mouse. It has no p27.
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