Checkpoints - Checkpoints Cancer checkpoint specific points where cell cycle can be put on hold 2 irreversible points replication of genetic material

Checkpoints, Cancer checkpoint - specific points where cell cycle can be put on hold • 2 irreversible points - replication of genetic material, sister chromatid separation • kinase - adds phosphate • phosphatase - takes away phosphate • phosphorylation/dephosphorylation >> activate/deactivate proteins >> drives cell cycle • cyclin - proteins displaying characteristic patterns of synthesis/degradation like the cell cycle • cyclin-dependent kinase (Cdk) - enzyme that controls passage through the checkpoints • multicellular organisms respond to more external signals and use more Cdk’s than unicellular organisms G1/S checkpoint - main point where the cell decides whether or not to divide • links cell division to cell growth • aka “restriction point” (R point) in animals • aka “start” in yeasts • decision to replicate genome >> decision to replicate • internal signals - nutritional cell state, cell size • external signals - factors that promote cell growth/division G2/M checkpoint