L13 - Chapter 17 The Cell Cycle A The mechanical events...

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Chapter 17: The Cell Cycle A) The mechanical events: Pages: 1053-55; 1070-71; 1075-87;1089; 1092-97 and from different chapters: 1034-5; 243-235, 595 B) The regulatory events
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The mechanical events of the cell cycle that allow nuclear division ( mitosis ) and cytoplasmic division ( cytokinesis ) Focus on how a cell accurately separates and distributes its chromosomes, which have been replicated in the preceding S phase, to daughter cells. Remember each daughter has to receive an identical copy. All eukaryotes solve this problem in a similar way--they assemble cytoskeletal machines that pull apart the duplicated chromosomes and then split the cytoplasm in half.
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The events of eucaryotic cell division as seen under a microscope
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The events of eucaryotic cell division as seen under a microscope
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0) Replication & preparation 1) Condensation 1) Mitotic spindle assembles 2) Nuclear envelope breakdown. Spindle attachment 3) Align at equator 4) Separation 6) Nuclear envelop reassembles 7) Cytokinesis 5) Separation
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Movie demonstrating mitosis in Drosophila filmed by UC professor Bill Sullivan
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Interphase: Preparation for Segregation: Two members of a family of proteins called SMC proteins-- Structural Maintenance of Chromosomes-- play critical roles: 1) Cohesin and 2) Condensin Basic unit form the ring: Coiled-coil protein with ATPases at either end that come together due to a hinge region that folds the two long coiled-coil regions together
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Human mitotic chromosomes stained to reveal the condensin complex A) Mitotic chromosome B) Metaphase chromosome The sister chromatids are separated by breaking up cohesins although enough cohesin is left to keep the chomatids together at the centromere until anaphase While the condensins ensure that each individual sister chromatid is organized and condensed.
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Cohesin : 4 subunit protein complex: Smc1, Smc3: coiled coil proteins Scc1, Scc3: connecting protein Cohesins form a ring around the two sister chromatids to keep them organized
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Condensin : 5 subunit protein complex: Smc2, Smc4: coiled coil proteins CAP-G, CAP-H, CAP-D2: connecting protein
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Human mitotic chromosomes stained to reveal the condensin complex A) Mitotic chromosome B) Metaphase chromosome The sister chromatids are separated by breaking cohesins although enough cohesin is left to keep the chomatids together at the centromere until anaphase While the condensins ensure that each individual sister chromatid is organized and condensed.
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The centrosome duplicates Remember the pair of centrioles in the amorphous cloud Interphase ( S phase ) : preparation for segregation:
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Electron micrograph showing the duplicated centrosome. There are now two centrioles but they remain in one complex. Check out how you section one cross-wise and one longitudinally-this is how we know that they are aligned at right angles to each other The centrosome duplicates
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The centrosome cycle: The centrioles replicate by a completely mysterious process The centrosome replicates
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Mother: more complex Daughter: smaller and simpler The daughter centrosome is less complex than mother centrosome
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