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68 Cards in this Set

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  • Back
Microtubule instability ____ greatly at ____
increases greatly at M Phase
core control for cell cycle?
CDK
what are the cdk levels in g1
completely inactive
missing
MT dynamics
what happens to number and half-life and what does it undergo
the number goes up but the half-life goes down

undergo catastrophe
also true for signaling
how does cell-cyle control system trigger these dramatic changes in the cell's MTs at the onset of mitosis?
prophase signals an abrupt change in cell MTs
MTs
random facts
more of them, shorter, undergo rapid growth and catastrophe
balance btw ___ and ____ influences the
balance btw catastrophins and MAPs influences the Frequency of catastrophes and length of MTs
M-cdk phosphorylates ____
MT motor, MAPs
catastrophins promote
breakdown
there is a balance btw
growth and catastrophe
MAPs stabilize
MTs
MT spindles are not properly formed,
lack spindle polarity at all when not a balance
interaction btw ____ and ____ of opposite polarity drive ____
interaction btw opposing motor proteins and MTs of opposite polarity drive spindle assembly
we align anti-parallel to promote
sliding
MT motors
2 things you need
absolutely must have motors
need both plus end directed and minus end directed
plus end is the ____ end
lengthening of the signal
motors are important to ____
promote sliding and lengthening as well as promoting foci
model for spindle assembly is driven by
motors and polarity
motors are associated with ____
overlapping
spindle checkpoint because proteins in black determine
whether or not it is properly attached
MT will be added near which end?
the plus end
specialized motors move to which end
the plus end
capturing kinetochores
a)
unattached chromosome at prometaphase
b
one kinetochore binds laterally to an astral MT
c
chromosome slides toward spindle pole
d
lateral attachment converts to end-on, unipolar attachment, MT now called kinetochore MT
e
free kinetochore captures MTs from opposite spindle pole to convert unipolar to bipolar attachment
MT attachment
the plus end does not make direct contact with kinetochore
what does the collar do?
holds them close but plus end and kinetochore not directly attached
-growth and attachment can occur
-each site is thought to contain collar
search and capture
1st thing is that these chromosomes are floating around
-sends out searching MTs that grow and shrink, increasing prob. that it will capture
-sensing mechanism
-lateral attachment of kinetochore
why do we need growth here?
to push it to the middle of the cell
why is the collar so critical?
because it allows for catastrophe
the kinetochore =
"tug of war"
both + and - end directed MTs
anaphase is delayed until all chromosomes are positioned at the
metaphase plate
high level of synchrony
you need info to show that all of them are attached
-syncroning within a cell and somehow surrounding cells
anaphase A
chromatid separation
how do we get chromatid separation
anaphase A
and apc
apc
-cleaves and inactivates m-cdk
-cleaves securin and activates separase
-securin: keeps separase (need active separase to cleave sister chromatids
-degradation of cohesin
poleward movement and ____
shortening of kinetochore MT
anaphase a
depends on ____ at ___
depends on motor proteins at kinetochore
anaphase A steps
shortening of kinetochore MTs; movement of daughter chromosomes to poles; forces generated mainly at kinetochores
how do we get movement in anaphase a?
by depolarization and also by motors in kinetochore
movement by depolarization and also by motors in kinetochore ensures ___
movement to opposite end of cell to get ready for cytokinesis
poleward force generation models
ATP-driven motor protein drives both ____
chromosome movement and MT disassembly
MT disassembly drives ___
chromosome movement
there are two models of poleward force
1 is active, has ATP-driven motor protein which drives both chromosome movement and mt disassembly
the passive poleward force generation model moves by
MT disassembly
anaphase B pole separation
depends on motor proteins at poles (pull) and
depends on motor proteins at central spindle (push)
in anaphase B these are not ___
kinetochore
-overlapping instead
-pushing and pulling of MT via + and - end motors
in anaphase B a sliding force is generated btw
btw overlap MTs from opposite poles to push the poles apart
both pushing and pulling forces contribute to anaphase B
outward push on spindle poles and outward pull on spindle poles
____ are connected to cell cortex by minus-end motors (which are not moving)
astral MTs
-thus there is a pulling effect
what has greater overlap
metaphase or anaphase?
metaphase
anaphase has much smaller overlap
telophase
chromosome decondensation and nuclear membrane reformation
interphase to prophase
phosphorylation of lamins
prophase to telophase
dephorylation of lamins
telophase to interphase nucleus
fusion of nuclear envelope vesicle
early cleavage of frog embryo
furrowing caused by
activity of contractile ring underneath the cell membrane
normally, ____ determines where cleavage occurs and when
mitotic spindle
furrowing occurs in _____
plane of metaphase plate, at right angles to the long axis of the mitotic spindle
contractile ring assembles
early in anaphase
different from pushing/pulling
cleavage furrow 'pinching'
cleavage furrow is mediated by
myosin II which is only in contractile ring
daughter cells have a ____ which is remnants of ___
midbody which are remnants of MT spindle
what is dense matrix material?
tells us we don't know everything
enriched in signaling proteins
-in dense materials, there are rho's, ROCK
rhoA is a small ____
GTPase
has gaps which hydrolyze GTP to GDP
regulation of contractile ring by
GTPase RhoA
the active GTP-bound form of RhoA is focused at ____
the future cleavage site
there are 3 models for influencing c-ring orientation (2 are active)
actives: astral stimulation model and central spindle stimulation model
passive: astral relaxation model