29 separation of chromosomes during anaphase requires

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Separation of chromosomes during Anaphase requires MT motors Dynein/dynactin at centromeric region pull towards MTOC (-) end of MT spindle (spindle pole) on astral MT pull MTOC to cell periphery Kinesins connect chromosome arms to polar MT bipolar kinesin pushes polar MT apart Depolymerization at (+) and (-) end 30
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Sister chromatid connected and aligned during replication Cohesin complex coats DNA keeps replicating sister chromatid in close proximity Only remain at centromere (center of chromosome) of each chromosome Cohesin complexes replaced by condensin proteins which facilitate condensation and packing of the DNA 31
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Cohesion of chromatids at centromere is tightly regulated Cohesin - multi-protein complex (smc1, smc3, and kleisin) that holds sister chromatid together; remains at centromeres Separase - enzyme that cleaves part of cohesin to release chromosomes prior to separation Securin - inhibits separase thus ensuring proper timing of chromosome separation 32
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Ubiquitin-mediated protein degradation Ubiquitin- 8.5kD protein found ubiquitiously E1- Ubiquitin-activating enzyme E2- Ubiquitin conjugating enzyme E3- recognizes substrate; transfers ubiquitin to target Substrate- contains amino acid destruction sequence Proteosome- recognizes ubiquitin destruction “flag”; shreds protein 33
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What happens when MPF is active? DNA condenses MT spindle starts to form Chromosomes align MT spindle at poles Chromosomes separate MT spindle separates DNA decondenses MT spindle disassembles 34
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What happens when M-cyclin is resistant to destruction? DNA condenses MT spindle starts to form Chromosomes align MT spindle at poles Chromosomes separate MT spindle separates DNA stays condensed MT spindle remains intact 35
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What happens when M-cyclin destruction system is overwhelmed by excessive destruction box peptides? Observation: No chromosome separation Sister chromatids remain attached Different phenotype than non-degradable M-cyclin Is there another substrate for the late mitosis destruction complex? 36
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Ubiquitin-mediated protein degradation in Anaphase Degradation of proteins dictates the forward movement of the cell cycle 37 Cdh1- M-cyclin Cdc20- securin
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