Chapter 17 Notes - Chapter 17: The Cell Cycle Overview of...

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Chapter 17: The Cell Cycle Overview of the Cell Cycle -Divided into four phases: S phase, M phase, G1 phase, and G2 phase -S phase: chromosome duplication -M phase: chromosome segregation and cell division (mitosis + cytokinesis) -G1 phase: between M and S phase; growth and monitoring of internal/external environment -G2 phase: between S and M phase -G0 phase: resting state where no cell division takes place No G1 or G2 phase during cell division of fertilized egg in a frog egg. Cell-Cycle Control System -triggers the major events of the cell cycle -possesses many biochemical molecular switches -the switches are binary and launch events in a complete fashion (nothing partial) -is robust and reliable due to the backup mechanisms it has -is highly adaptable to suit certain cell types or respond to certain signals Three major checkpoints: 1. Start/restriction point : cell-cycle entry and chromosome duplication 2. G2/M checkpoint -triggers early mitotic events such as metaphase 3. Metaphase-to-anaphase transition -stimulates chromatid separation (anaphase), leading to completion of mitosis and cytokinesis The control system can block progression through each checkpoint if it detects problems inside or outside the cell. Cyclin-Dependent Protein Kinases (Cdks) -phosphorylate intracellular proteins that regulate the events of the cell cycle -depend on cyclin for their protein kinase activity -cyclin-Cdk complexes trigger cell cycle events -Cyclin also directs its Cdk partner to specific target proteins Four classes of cyclins -G1/S-cyclins : activate Cdks in late G1 and trigger progression through Start, resulting in a commitment to cell-cycle entry -S-cyclins : bind Cdks after Start and help stimulate chromosome duplication and other
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This note was uploaded on 11/11/2010 for the course BIO 320 taught by Professor Staff during the Fall '08 term at University of Texas at Austin.

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Chapter 17 Notes - Chapter 17: The Cell Cycle Overview of...

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