Lecture 15-16, cell cycle, 19F.pdf - Cell cycle Ordered series of events that lead to cell division and the production of two daughter cells(i.e cell

Lecture 15-16, cell cycle, 19F.pdf - Cell cycle Ordered...

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genetically identical Cell cycle: Ordered series of events that lead to cell division and the production of two daughter cells (i.e, cell proliferation)
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Major control points of the cell cycle in most animal cells: G1 to S (Start) G2 to M metaphase to anaphase Figure 17-4 Molecular Biology of the Cell (© Garland Science 2015) (Gap 1) (Gap 2) Some rapidly dividing cells (e.g., early embryonic cells) don’t have G1 and G2, and gets smaller with with each cell cycle G 0 Start (or restriction point), commitment point after which cell progresses into S phase independent of signals from environment (Genome duplication) (partitioning of duplicated genome) For most cell types, growth in cell size occurs mostly in G1 long long shorter very short
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The Nobel Prize in Physiology or Medicine for 2001 was awarded jointly to Leland Hartwell, Timothy (Tim) Hunt and Paul Nurse for their discoveries of "key regulators of the cell cycle"
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In most cells, checkpoint mechanisms ensure orderly progression through the cell cycle Figure 17-9 Molecular Biology of the Cell (© Garland Science 2015) Many other conditions that are surveyed are not shown here Is DNA damaged? Is DNA damaged? Is cell big enough? Checkpoints survey conditions inside and outside the cell and halt cell cycle progression until appropriate conditions have been met.
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Figure 17-10 Molecular Biology of the Cell (© Garland Science 2015) Checkpoints control activities of different c yclin- d ependent k inase (Cdk) complexes, which drive progression through different cell cycle stages Each Cdk complex has two subunits: 1) a kinase subunit that is INACTIVE alone, and its abundance is roughly constant through the cell cycle (in most cell types). 2) a cyclin subunit that fluctuates in abundance through the cell cycle. It binds and is needed to activate the kinase subunit. It also determines the substrate specificity of Cdk complex.
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Activation of a Cdk requires not only its binding to an appropriate cyclin BUT ALSO phosphorylation of Cdk at a specific site by the C dk-a ctivating k inase (CAK) Figure 17-12 Molecular Biology of the Cell (© Garland Science 2015) T-loop (a.k.a. activation loop) blocks access of substrate to active site (not regulated) CAK is always present and active.
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