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Mitosis and Meiosis 92607

Mitosis and Meiosis 92607 - Mitosis and Meiosis 1 Cell...

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Mitosis and Meiosis 1. Cell cycle for most cells has two phases: Division and Interphase Interphase has three sub-phases: G 1 ---S---G 2 Division: Mitosis or Meiosis and Cytokinesis Purpose of G 1 prepare for S (may at some point go to G 0 ) Therefore, G 1 can be thought of as a transition phase Problem: How are decisions made? Must activate proteins called Cyclin-dependent Kinases or Cdk’s Cdk’s catalyze the phosphorylation of specific (target) proteins. How is Cdk activated? Another protein binds to it, Cyclin forming what is termed a Cyclin- Cdk complex that then acts as a protein kinase and triggers the transition from G 1 to S. (INSIDE THE CELL****) However, major point!!!!!!!!!!!!!!!! One more substance is necessary to complete the transition!!!!!!!!!!!!!!!! Retinoblastoma protein, otherwise known as (RB). RB is an inhibitor that then must be inhibited!!!!!! Yes Cdk’s phosphorylate RB which then becomes inactive and only then can G 1 move to S Why so significant? Well, over stimulation (production of Cdk) leads to more inhibition of RB which then can lead to an over production of new cells.
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