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30 Cards in this Set
- Front
- Back
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Four phases of the eukaryotic cell cycle
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G1
S (DNA replication) G2 M (mitosis + cytokinesis) |
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What are gap phases?
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they are pauses that llow the cell to grow and respond to environmental cues
cells can enter g0, a noncyclinc, resting state, until environmental conditions are more favorable |
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6 stages of the M phase
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1. prophase
2. prometaphase 3. metaphase 4. anaphase 5. telophase 6. cytokinesis |
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Interphase
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the cell increases in size
DNA is replicated centrosome is duplicated |
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Prophase
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chromosomes condense
spindle migration continues microtubule dynamic instability increases |
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Prometaphase
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nuclear envelope breaks down
chromosomes attach to microtubules |
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Metaphase
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alignment of the microtubule-attached chromosomes at the metaphase plate
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Anaphase
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sister chromatids separate
kinetochore microtubules get shorter and pull chromasomes apart |
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Telophase
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daughter chromosomes arrive at the poles,
nuclear envelope reforms, contractile ring begins to assemble |
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Cytokinesis
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cytoplasm is divide din two by the contractile ring
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The ____ cytoskeleton and molecular motors ___ and __ are actively used to do work during mitosis
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microtubule cytoskeleton
motors kinesin and dynein |
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What 3 classes of microtubules form the mitotic spindle?
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microtubules:
1. astral 2. kinetochore 3. overlap/interpolar |
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Major motor proteins of the mitotic spindle
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kinesin-5
kinesin-14 kinesin-4,10 dyneins |
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Kinesin 5
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bipolar, plus-end directed motor
pushes spindles apart |
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Kinesin 14
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minus-end directed
pull spindles toward one another |
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Kinesin 4,10
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conventional plus-end directed
attach chromosomes to MTs for positioning |
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Dyneins' role in the mitotic spindle
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attach the astral MTs to the cell periphery
pull spindles apart as they walk towards the minus end of MTs |
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Kar3p
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a kinesin 14, minus end motor protein
too much = short spindles |
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Cin8p
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a kinesin 5, plus end motor protein
too much makes long spindles |
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What do catastrophins and MAPs do?
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they determine mitotic microtubule length
- MAPs stabilize MTs - catastrophins increase instability |
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How do mitotic chromosomes promote bipolar spindle assembly?
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1. nucleation
2. antiparallel cross-linking (by kinesin 5) 3. outward push (kinesin 4,10) 4. focusing of poles by (dynein and kinesin 14) |
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What forces move chromosomes on the spindle?
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1.kinetochore generated poleward force
- plus-end depolymerization - free protofilaments curl outword and push against the collar 2. poleward microtubule flux - tubulin removal begins at the kinetochore 3. polar ejection force - kinesins-4,10 attach to chromosomes at their ends and push away |
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Explain microtubule flux
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tubulin addition towards the kinetochore stops at the metaphase/anaphase tramsotopm
tubulin removal |
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Steps of cytokinesis
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intiation
contraction membrane insertion completion |
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ESCRT ___ is required for cytokinesis
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ESCRT III
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Local activation of RhoA trigger assembly and contraction of the contractile ring
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inactive RhoA triggered by RhoGEF --> active RhoA
---> 1) formin --> actin filament formation ----> 2) Rho-activated kinases --> myosin light-chain phosphorylation --> myosin II activation |
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What is centrisome duplication triggered by?
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activation of the G1/S-Cdk complex at the beginning of the S-phase
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Xmap125
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stabilizes MTs during mitosis; removal of Xmap125 increases instability and shortens MT length
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Mcak
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a catastrophin, a kinesin-related protein, increases MT turnover during mitosis
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Rock
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Rho-activated kinase, promotes myosin activation by RhoA downstream activation
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