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BIO107 - CELL AND MOLECULAR BIOLOGY > Cell cycle (Mitosis) > Flashcards

Cell cycle (Mitosis) Flashcards

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1
Q

At prophase

A
  1. the replicated chromosomes, each
    consisting of two closely associated sister chromatids, condense
  2. Outside the nucleus, the mitotic spindle
    assembles between the two centrosomes, which have replicated and moved apart.
  3. In diploid cells, there would be
    two copies of each chromosome present
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2
Q

At prometaphase

A
  1. starts abruptly with the breakdown of the nuclear envelope
  2. Chromosomes can now attach to spindle
    microtubules via their kinetochores and undergo active movement.
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3
Q

At metaphase

A
  1. the chromosomes are aligned at the equator of the spindle, midway between
    the spindle poles.
  2. The kinetochore microtubules attach sister chromatids to opposite poles of the
    spindle.
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4
Q

At anaphase

A
  1. the sister chromatids synchronously separate to form two daughter chromosomes,
    and each is pulled slowly toward the spindle pole it faces.
  2. The kinetochore microtubules get shorter,
    and the spindle poles also move apart; both
    processes contribute to chromosome segregation.
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5
Q

During telophase

A
  1. the two sets of daughter chromosomes arrive at the poles of the spindle and decondense.
  2. A new nuclear envelope reassembles around each set, completing the formation
    of two nuclei and marking the end of mitosis. 3. The division of the cytoplasm begins with contraction of the contractile ring
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6
Q

During cytokinesis

A
  1. the cytoplasm is divided in two by a contractile ring of actin and myosin
    filaments, which pinches the cell in two to create two daughters, each with
    one nucleus.
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7
Q

induce the assembly of the mitotic spindle and ensure that each sister chromatid in a pair is attached to the opposite pole of the spindle

A

M-Cdk

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8
Q

M-Cdk induce the assembly of the ____ ____ and and ensure that each sister chromatid in a pair is attached to the ____ ____ of the ____

A

mitotic spindle
opposite pole of the spindle.

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9
Q

triggers chromosome condensation

A

M-Cdk

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10
Q

promotes the breakdown of the nuclear envelope and rearrangements of the actin cytoskeleton and the Golgi apparatus

A

M-Cdk

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11
Q

2 phosphorylation of specific proteins

A

Polo-like kinase (Plk)
Aurora kinases

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12
Q

required for the normal assembly of a
bipolar mitotic spindle

A

Polo-like kinase (Plk)

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13
Q

2 types of Aurora kinases

A

A
B

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14
Q

helps control proteins that govern the
assembly and stability of the spindle

A

A

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15
Q

controls attachment of sister chromatids to the spindle

A

B

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16
Q

begins with the accumulation of M-cyclin

A

M-Cdk activation

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17
Q

stockpile of M-Cdk

A

Cdk-activating kinase (CAK) and
inhibitory protein kinase Wee1

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18
Q

removes inhibitory phosphatase that
restrain M-Cdk

A

activation of phosphatase Cdc25

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19
Q

activation of phosphatase Cdc25 removes inhibitory phosphatase that
restrain _-___

A

M-Cdk

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20
Q

inhibitory activity of the kinase ____ is
suppressed

A

Wee1

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21
Q

suggests that M-Cdk activation in mitosis involves positive feedback loops

A

ability of M-Cdk to activate its own activator (Cdc25) and inhibit its own inhibitor (Wee1)

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22
Q

activator of M-Cdk

A

Cdc25

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23
Q

inhibitor of M-Cdk

A

Wee1

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24
Q

chromatids are compacted

A

chromosome condensation

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25
Q

two sisters are resolved into distinct, separable units

A

sister-chromatid resolution

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26
Q

condensation and resolution of sister chromatids depend on a five-subunit protein complex called

A

condensin

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27
Q

holds sister chromatids

A

Condensin

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28
Q

What does condensin contains?

A

two SMC subunits plus three non-SMC
subunits

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29
Q

Condensin may form a ______ structure that
somehow uses the energy provided by ATP hydrolysis to promote the _____
and _____of sister chromatids.

A

ringlike
compaction and resolution

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30
Q

depends on mitotic spindle

A

chromosome segregation

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31
Q

triggers the assembly of the spindle
early in mitosis

A

M-Cdk

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32
Q

Spindle formation in animal cells depends
largely on the ability of motor proteins to organize ?

A

bipolar array of microtubules

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33
Q

overlapped with the plus ends of microtubules from the other pole

A

interpolar microtubules

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34
Q

attached to sister-chromatid pairs at large protein structures called kinetochores

A

kinetochore microtubules

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35
Q

radiate outward from
the poles and contact cell cortex

A

astral microtubules

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36
Q

consists of a cloud of pericentriolar matrix that surrounds a pair of centrioles

A

centrosome

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37
Q

Each centrosome
consists of a cloud of amorphous material called the

A

pericentriolar matrix

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38
Q

pericentriolar matrix contains a
variety of proteins, including ______-____ motor proteins, _____-____ proteins that link the motors to the centrosome, ____ proteins, and components of the ___-____ ____ ___

A

microtubule-dependent
coiled-coil
structural
cell-cycle control system.

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39
Q

contains γ-tubulin ring complexes

A

pericentriolar matrix

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40
Q

microtubule-dependent motor protein depends on?

A

kinesin-related proteins and dyneins

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41
Q

usually move toward the plus end
of microtubules

A

kinesin-related proteins

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42
Q

move toward the minus end

A

dyneins

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43
Q

Four major types of motor proteins

A

kinesin-5, kinesin-14, kinesins-4/10,
and dynein

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44
Q

move toward the plus ends of the microtubules, they slide the two antiparallel microtubules past each other toward the spindle poles, pushing the
poles apart

A

kinesin-5

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45
Q

are minus-end directed motors; cross-link antiparallel interpolar microtubules at the spindle midzone and tend to pull the poles together

A

kinesin-14

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46
Q
  • minus-end directed motors
  • cross-link antiparallel interpolar microtubules at the spindle midzone and tend to pull the poles together
A

kinesin-14

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47
Q

-also called chromokinesins
-plus-end directed motors that associate with chromosome arms and push the attached chromosome away from the pole

A

kinesin-4/10

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48
Q

kinesin-4/10 are also called ?

A

chromokinesins

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49
Q
  • minus-end directed motors
  • motors pull the spindle poles toward the cell cortex and away from each other
A

dynein

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50
Q

mitotic spindle must have two poles

A

bipolarity of spindle

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51
Q

enters mitosis with a pair of centrosomes

A

depends on centrosome

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52
Q

Spindle formation depend on the ability of mitotic chromosomes to ____ and ____microtubules and on the ability of motor proteins to organize
microtubules into a ___array

A

nucleate
stabilize
bipolar

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53
Q

centrosome duplicates when the cell
enters the?

A

cell cycle – S phase

54
Q

helps initiate centrosome
duplication

A

G1/S-Cdk

55
Q

separate, and each nucleates the
formation of a single new centriole

A

two centrioles in the centrosome

56
Q

two centrioles in the centrosome
separate, and each nucleates the
formation of a single new centriole, resulting in

A

two centriole pairs within an enlarged
pericentriolar matrix

57
Q

mechanism of duplication use by both centrosome duplication and chromosome duplication

A

semiconservative mechanism of
duplication

58
Q

must replicate once and only once per
cell cycle

A

Centrosomes

59
Q

spindle assembly begins in?

A

early mitosis

60
Q

pulled by dynein motor proteins that link ___ microtubules to the cell
cortex

A

astral

61
Q

plus ends of the microtubules between the centrosomes interdigitate to
form the

A

interpolar microtubules

62
Q

the number of γ-tubulin ring
complexes in each centrosome increases greatly, increasing the ability of the centrosomes to nucleate new microtubules, a process called

A

centrosome maturation

63
Q

generally promote centrosome separation and
increase spindle length

A

dynein and kinesin-5 motors

64
Q

phosphorylate kinesin-5 motors

A

M-Cdk and Aurora-A

65
Q

located in the cytoplasm

A

centrosomes and microtubules

66
Q

located in the nucleus

A

chromosomes

67
Q

allowed the attachment of sisterchromatid pairs to the spindle

A

removal of nuclear membrane

68
Q

begin when M-Cdk phosphorylates several subunits of the nuclear pore
complexes

A

Nuclear-envelope breakdown

69
Q

M-Cdk also phosphorylates components of the

A

nuclear lamina

70
Q

microtubules are either catastrophe or rescue

A

microtubule dynamic instability

71
Q

switch from growth to shrinkage

A

catastrophe

72
Q

shrinkage to growth

A

rescue

73
Q

Signals ann abrupt change in the cell’s microtubules

A

Entry into mitosis

74
Q

emanating from both centrosomes

A

larger number of shorter and more dynamic microtubules

75
Q

half-life in microtubule decreases

A

prophase, prometaphase, metaphase

76
Q

increase in microtubule instability, coupled with the increased ability
of centrosomes to nucleate microtubules results in remarkably dense and dynamic arrays of _____ _____ that are ideally suited for capturing _____ ______

A

spindle microtubules
sister chromatids

77
Q

promote stability and
catastrophe factors that destabilize microtubule plus ends

A

microtubule-associated proteins (MAPs)

78
Q

chromosomes play an active part in spindle
formation bycreating a local environment
that favors both

A

microtubule nucleation and
microtubule stabilization

79
Q

bound to the chromatin

A

guanine nucleotide exchange factor

80
Q

guanine nucleotide exchange factor (GEF) that is bound to chromatin ->

A

activated Ran-GTP – releases microtubule-stabilizing proteins

81
Q

guanine nucleotide exchange factor (GEF) that is bound to chromatin ->activated Ran-GTP – releases microtubule-stabilizing proteins->

A

nucleation and stabilization of
microtubules around chromosomes

82
Q

the ability of chromosomes to stabilize and
organize microtubules enables cells to form

A

bipolar spindles in the absence of
centrosomes

83
Q

use this chromosome-based self-organization process to
form spindles

A

higher plants, animal oocytes, animal
embryos develop from eggs without
fertilization

84
Q

second major step
in spindle formation

A

attachment of the array to the sister-chromatid pairs

85
Q

a giant, multilayered
protein structure that is built at the
centromeric region of the chromatid

A

kinetochore

86
Q

embedded head-on in specialized
microtubule attachment sites

A

plus ends of kinetochore microtubules

87
Q

rod-shaped protein complex;
linking the microtubule to the
kinetochore

A

Ndc80

88
Q

most initial attachments

A

unstable lateral attachments

89
Q

unstable lateral attachments, in which _____attaches to the
side of the passing _____

A

kinetochore
microtubule

90
Q

dynamic microtubule plus ends capture the ____ in the correct ___-__ orientation

A

Kinetochores
end-on

91
Q

microtubules in the vicinity of the chromosomes become
embedded in the plus-end-binding sites of the kinetochore in the absence of?

A

absence of centrosome

92
Q

Polymerization at plus-end-binding sites of the kinetochore then results in growth of the ______ away from the _____.

A

microtubules
kinetochore

93
Q

sister chromatids in a pair attach to opposite poles of the mitotic spindle

A

bi-orientation

94
Q

What prevents the attachment of both kinetochores to the same
spindle pole or the attachment of one kinetochore to both spindle poles?

A

sister kinetochores are constructed in a back-to-back orientation that reduces the likelihood that both kinetochores can face the same spindle
pole.

95
Q

corrected by a
system of trial and error

A

incorrect attachments

96
Q

highly unstable
and do not last

A

incorrect attachments

97
Q

how does the kinetochore sense a correct
attachment?

A

tension
When a sister-chromatid pair is properly bi-oriented on the spindle, the two kinetochores are pulled in opposite directions by strong poleward forces. Sister-chromatid cohesion resists these poleward forces, creating high levels of tension within
the kinetochores

98
Q

when both sister chromatids are attached
to the same spindle pole →

A

low tension
within the kinetochores

99
Q

when both sister chromatids are attached
to the same spindle pole → low tension
within the kinetochores →

A

sends an
inhibitory signal that loosens the
attachment

100
Q

tension-sensing mechanism depends on the
protein kinase ?

A

Aurora-B

101
Q

depends on the
protein kinase Aurora-B

A

tension-sensing mechanism

102
Q

generate the inhibitory signal that reduces the
strength of microtubule attachment in the
absence of tension

A

Aurora-B

103
Q

phosphorylate some components at microtubule
attachment site →

A

decrease affinity for
microtubule plus end

104
Q

initiates sister-chromatid separation by
ubiquitylating several mitotic regulatory
proteins and thereby triggering their
destruction

A

anaphase-promoting complex (APC/C)

105
Q

anaphase-promoting complex (APC/C)initiates sister-chromatid separation by
_____ several mitotic ____
proteins and thereby triggering their
____

A

ubiquitylating
regulatory
destruction

106
Q

cohesins hold sister
chromatids together

A

metaphase

107
Q

loss of sister-chromatid
cohesion

A

anaphase

108
Q

APC/C target ____ (inhibitory protein)
for destruction

A

securin

109
Q

securin binds to and inhibits the activity
of a protease called

A

separase

110
Q

separase cleave subunits of

A

cohesin

111
Q

APC/C also targets the _- and _-____for destruction leading to Cdk inactivation

A

S- and M-cyclins

112
Q

allows phosphatases to
dephosphorylate the many Cdk target
substrates in the cell, as required for the
completion of mitosis and cytokinesis

A

Cdk inactivation

113
Q

blocks
progression through the metaphase-toanaphase transition

A

spindle assembly checkpoint

114
Q

spindle assembly checkpoint mechanism ensures that cells do not enter _____
until all chromosomes are correctly bi-oriented on the ____ ___

A

anaphase
mitotic spindle

115
Q

not properly attached kinetochore →

A

blocks Cdc20-APC/C activation

116
Q

not properly attached kinetochore →
blocks Cdc20-APC/C activation →

A

blocks the metaphase-to-anaphase
transition

117
Q

unattached kinetochore acts like
an enzyme that catalyzes a change in
the conformation of Mad2

A

Mad2

118
Q

unattached kinetochore acts like
an enzyme that catalyzes a change in
the conformation of Mad2 →

A

can bind
and inhibit Cdc20–APC/C

119
Q

sudden loss of sister-chromatid cohesion at
the onset of anaphase →

A

chromosome
segregation

120
Q

initial poleward movement
of the chromosomes

A

anaphase A

121
Q

Chromosome movement in anaphase A depends on a combination of the two
major poleward forces :

A
  1. microtubule depolymerization at the
    kinetochore
  2. microtubule flux- poleward
    movement of the microtubules
122
Q

separation of the spindle
poles themselves

A

anaphase B

123
Q

the two sets of chromosomes are packaged into a
pair of daughter nuclei

A

telophase

124
Q

disassembly of mitotic spindle → r

A

reformation of the nuclear
envelope

125
Q

promotes spindle assembly,
chromosome condensation, and nuclear envelope breakdown

A

phosphorylation by M-Cdk

126
Q

phosphorylation by M-Cdk promotes?

A

spindle assembly,
chromosome condensation, and nuclear envelope breakdown

127
Q

spindle disassembly and the re-formation of
daughter nuclei

A

dephosphorylation

128
Q

could be
triggered by the inactivation of Cdks, the activation of
phosphatases, or both

A

dephosphorylations and the completion of mitosis

129
Q

dephosphorylations and the completion of mitosis could be
triggered by the

A

inactivation of Cdks, the activation of
phosphatases, or both

130
Q
A

BIO107 - CELL AND MOLECULAR BIOLOGY (16 decks)

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