Cell Bio Lecture 37

Front 1

Microtubule instability ____ greatly at ____

Back 1

increases greatly at M Phase

Front 2

core control for cell cycle?

Back 2

CDK

Front 3

what are the cdk levels in g1

Back 3

completely inactive
missing

Front 4

MT dynamics
what happens to number and half-life and what does it undergo

Back 4

the number goes up but the half-life goes down

undergo catastrophe
also true for signaling

Front 5

how does cell-cyle control system trigger these dramatic changes in the cell's MTs at the onset of mitosis?

Back 5

prophase signals an abrupt change in cell MTs

Front 6

MTs
random facts

Back 6

more of them, shorter, undergo rapid growth and catastrophe

Front 7

balance btw ___ and ____ influences the

Back 7

balance btw catastrophins and MAPs influences the Frequency of catastrophes and length of MTs

Front 8

M-cdk phosphorylates ____

Back 8

MT motor, MAPs

Front 9

catastrophins promote

Back 9

breakdown

Front 10

there is a balance btw

Back 10

growth and catastrophe

Front 11

MAPs stabilize

Back 11

MTs

Front 12

MT spindles are not properly formed,

Back 12

lack spindle polarity at all when not a balance

Front 13

interaction btw ____ and ____ of opposite polarity drive ____

Back 13

interaction btw opposing motor proteins and MTs of opposite polarity drive spindle assembly

Front 14

we align anti-parallel to promote

Back 14

sliding

Front 15

MT motors
2 things you need

Back 15

absolutely must have motors
need both plus end directed and minus end directed

Front 16

plus end is the ____ end

Back 16

lengthening of the signal

Front 17

motors are important to ____

Back 17

promote sliding and lengthening as well as promoting foci

Front 18

model for spindle assembly is driven by

Back 18

motors and polarity

Front 19

motors are associated with ____

Back 19

overlapping

Front 20

spindle checkpoint because proteins in black determine

Back 20

whether or not it is properly attached

Front 21

MT will be added near which end?

Back 21

the plus end

Front 22

specialized motors move to which end

Back 22

the plus end

Front 23

capturing kinetochores
a)

Back 23

unattached chromosome at prometaphase

Front 24

b

Back 24

one kinetochore binds laterally to an astral MT

Front 25

c

Back 25

chromosome slides toward spindle pole

Front 26

d

Back 26

lateral attachment converts to end-on, unipolar attachment, MT now called kinetochore MT

Front 27

e

Back 27

free kinetochore captures MTs from opposite spindle pole to convert unipolar to bipolar attachment

Front 28

MT attachment

Back 28

the plus end does not make direct contact with kinetochore

Front 29

what does the collar do?

Back 29

holds them close but plus end and kinetochore not directly attached
-growth and attachment can occur
-each site is thought to contain collar

Front 30

search and capture

Back 30

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

Front 31

why do we need growth here?

Back 31

to push it to the middle of the cell

Front 32

why is the collar so critical?

Back 32

because it allows for catastrophe

Front 33

the kinetochore =

Back 33

"tug of war"
both + and - end directed MTs

Front 34

anaphase is delayed until all chromosomes are positioned at the

Back 34

metaphase plate

Front 35

high level of synchrony

Back 35

you need info to show that all of them are attached
-syncroning within a cell and somehow surrounding cells

Front 36

anaphase A

Back 36

chromatid separation

Front 37

how do we get chromatid separation

Back 37

anaphase A
and apc

Front 38

apc

Back 38

-cleaves and inactivates m-cdk
-cleaves securin and activates separase
-securin: keeps separase (need active separase to cleave sister chromatids
-degradation of cohesin

Front 39

poleward movement and ____

Back 39

shortening of kinetochore MT

Front 40

anaphase a
depends on ____ at ___

Back 40

depends on motor proteins at kinetochore

Front 41

anaphase A steps

Back 41

shortening of kinetochore MTs; movement of daughter chromosomes to poles; forces generated mainly at kinetochores

Front 42

how do we get movement in anaphase a?

Back 42

by depolarization and also by motors in kinetochore

Front 43

movement by depolarization and also by motors in kinetochore ensures ___

Back 43

movement to opposite end of cell to get ready for cytokinesis

Front 44

poleward force generation models
ATP-driven motor protein drives both ____

Back 44

chromosome movement and MT disassembly

Front 45

MT disassembly drives ___

Back 45

chromosome movement

Front 46

there are two models of poleward force

Back 46

1 is active, has ATP-driven motor protein which drives both chromosome movement and mt disassembly

Front 47

the passive poleward force generation model moves by

Back 47

MT disassembly

Front 48

anaphase B pole separation

Back 48

depends on motor proteins at poles (pull) and
depends on motor proteins at central spindle (push)

Front 49

in anaphase B these are not ___

Back 49

kinetochore
-overlapping instead
-pushing and pulling of MT via + and - end motors

Front 50

in anaphase B a sliding force is generated btw

Back 50

btw overlap MTs from opposite poles to push the poles apart

Front 51

both pushing and pulling forces contribute to anaphase B

Back 51

outward push on spindle poles and outward pull on spindle poles

Front 52

____ are connected to cell cortex by minus-end motors (which are not moving)

Back 52

astral MTs
-thus there is a pulling effect

Front 53

what has greater overlap
metaphase or anaphase?

Back 53

metaphase
anaphase has much smaller overlap

Front 54

telophase

Back 54

chromosome decondensation and nuclear membrane reformation

Front 55

interphase to prophase

Back 55

phosphorylation of lamins

Front 56

prophase to telophase

Back 56

dephorylation of lamins

Front 57

telophase to interphase nucleus

Back 57

fusion of nuclear envelope vesicle

Front 58

early cleavage of frog embryo
furrowing caused by

Back 58

activity of contractile ring underneath the cell membrane

Front 59

normally, ____ determines where cleavage occurs and when

Back 59

mitotic spindle

Front 60

furrowing occurs in _____

Back 60

plane of metaphase plate, at right angles to the long axis of the mitotic spindle

Front 61

contractile ring assembles

Back 61

early in anaphase
different from pushing/pulling
cleavage furrow 'pinching'

Front 62

cleavage furrow is mediated by

Back 62

myosin II which is only in contractile ring

Front 63

daughter cells have a ____ which is remnants of ___

Back 63

midbody which are remnants of MT spindle

Front 64

what is dense matrix material?

Back 64

tells us we don't know everything
enriched in signaling proteins
-in dense materials, there are rho's, ROCK

Front 65

rhoA is a small ____

Back 65

GTPase
has gaps which hydrolyze GTP to GDP

Front 66

regulation of contractile ring by

Back 66

GTPase RhoA

Front 67

the active GTP-bound form of RhoA is focused at ____

Back 67

the future cleavage site

Front 68

there are 3 models for influencing c-ring orientation (2 are active)

Back 68

actives: astral stimulation model and central spindle stimulation model
passive: astral relaxation model