Lecture 20 11

Lecture 20 11 - Lecture 20 11/30/07 Cell Cycle continued...

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Lecture 20 11/30/07 Cell Cycle continued – Checkpoints Cell Cycle Checkpoints cell asks questions -CDK activation is controlled by levels of cyclins G1/S Checkpoint Questions 1.) Is DNA damaged? 2.) Are environmental conditions favorable for replication? Cell does not want to proceed through S phase if DNA is damaged or if environment is not favorable (e.g. starvation not enough energy) Controlled by transcription factor E2F – protein required for cell to proceed from G1 to S E2F – normally not active because bound to RB o When it is upregulated, activates other genes required for the cell to enter into S phase o Required for DNA synthesis as well o Allows cell to enter in S phase by upregulating S phase genes and upregulating itself, so more genes are made for S phase RB – usually bound to E2F, keeps E2F inactive o When cell is ready to go to S phase, G1 cyclin increases o CDK phosphorylates RB, release E2F protein, cell S phase o RB is an example of a tumor suppressor gene o G1 Cyclin increase activate CDK CDK phosphorylates RB RB releases E2F cell proceed into S phase
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This note was uploaded on 07/21/2008 for the course BICD 110 taught by Professor Mel during the Fall '06 term at UCSD.

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Lecture 20 11 - Lecture 20 11/30/07 Cell Cycle continued...

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