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BIO 107 - Cell and Mol. Bio > Cell cycle > Flashcards

Cell cycle Flashcards

1
Q

stage where DNA synthesis occur

A

S phase

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2
Q

Stage where mitosis and cytokineses takes place

A

M phase

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3
Q

between M phase and S phase

A

G1 phase

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4
Q

between S phase and mitosis.

A

G2 phase

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5
Q

Sequential phases that creates Interphase

A

G1, S, G2

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6
Q

Cell growth occurs throughout the cell cycle, except during ___

A

Mitosis

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7
Q

provide time for the cell to monitor the internal and external environment to ensure that conditions are suitable and preparations are complete before the cell commits itself to the major upheavals of S phase and mitosis

A

Gap phases

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8
Q

Specialized resting state

A

G0

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9
Q

biochemical dissection of cell-cycle control mechanisms

A

Xenopus laevis (Italicized)

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10
Q

is useful for the genetic analysis of mechanisms underlying the control and coordination of cell growth and division in multicellular organisms

A

Drosophila melanogaster (italicize)

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11
Q

Several organisms used in the analysis of eukaryotic cell cycle

A
  • The budding yeast Saccharomyces cerevisiae
  • fission yeast Schizosaccharomyces pombe
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12
Q

thymidine analogs that incorporated DNA of dividing cells during the S-phase

A

BrdU (Bromodeoxyuridine)

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13
Q

allows the rapid and automatic analysis of large numbers of cells

A

Flow cytometer

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14
Q

operates much like a timer that triggers the events of the cell cycle in a set sequence

A

Cell-cycle control system

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15
Q

(on/off ) and launch events in a complete, irreversible fashion

A

Binary

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16
Q

Three regulatory transitions

A
  1. Start in late G1
  2. G2/M transition
  3. Metaphase-to-Anaphase transition
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17
Q

cell commits to cell-cycle entry and chromosome duplication

A

Start (restriction point) in late G1

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18
Q

triggers the early mitotic events that lead to chromosome alignment on the mitotic spindle in metaphase

A

G2/M transition

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19
Q

stimulates sister-chromatid separation; completion of mitosis and cytokinesis

A

Metaphase-to-anaphase

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20
Q

central components of cell-cycle control system

A

Cyclin-dependents kinases (Cdks)

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21
Q

are controlled by cyclins

A

Cdks

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22
Q

Four classes of cyclins

A
  • G1/S-cyclin
  • S-cyclins
  • M-cyclins
  • G1-cyclins
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23
Q

activate Cdks in late G1

A

G1/S-cyclin

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24
Q

bind Cdks soon after progression through Start and help stimulate chromosome duplication

A

S-cyclins

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25
Q

activate Cdks that stimulate entry to mitosis at the G2/M transition

A

M-cyclins

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26
Q

govern the activities of the G1/S-cyclins

A

G1-cyclins

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27
Q

How many Cdks in vertebrates

A

Four Cdks

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28
Q

four Cdks in Vertebrates

A
  • two – G1-cyclins
  • one – G1/S- and S-cyclins
  • one – S- and M-cyclins
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29
Q

active site in the Cdk protein is partly obscured by a protein loop

A

Absence of cyclin

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30
Q

causes the loop to move away from the active site, resulting in partial activation of the Cdk enzyme

A

Cyclin binding

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31
Q

a separate kinase, the Cdk-activating kinase (CAK), phosphorylates an amino acid near the entrance of the Cdk active site

A

Full activation

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32
Q

What happens when Cdk protein is partially obscured by a protein loop

A

Absense of cyclin

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33
Q

When the loop moved away from the active site, what will happen to Cdk?

A

Partial activation of Cdk enzyme

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34
Q

phosphorylates an amino acid near the entrance of the Cdk active site

A

Cdk-activating kinase (CAK)

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35
Q

a protein kinase that inhibits Cdk activity

A

Wee1 protein kinase

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36
Q

a phosphatases that dephosphorylates the site, increasing Cdk activity

A

Cdc25 phosphatases

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37
Q

inactivated cyclin-Cdk complexes

A

Cdk inhibitor proteins (CKIs)

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38
Q

The key regulator that Triggers the Metaphase-to-Anaphase Transition

  • a member of the ubiquitin ligase family of enzymes.
A

Anaphase-promoting complex/Cyclosome (APC/C)

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39
Q

protect the protein linkages that hold sister-chromatid pairs together in early mitosis; destroyed at metaphase

A

Securin

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40
Q

destruction inactivates
most Cdks in the cell; proteins are dephosphorylated

A

S- and M-cyclins

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41
Q

ubiquitin ligase; ubiquitylate CKI proteins in late G1; destruction of G1/S-cyclins in early S phase

A

SCF

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42
Q
  • increases in mid-mitosis and remains high through G1
  • changes in its association
    with an activating subunit
A

APC/C activity

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43
Q

APC/C activity depends on what subunits?

A
  • Cdc20 or Cdh1
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44
Q

substrate-binding subunits called F-box proteins; constant during cell cycle

A

SCF activity

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45
Q

in early animal embryos – cell-cycle depends exclusively on ____ _____ that involve the regulation of Cdks and ubiquitin ligases and their target proteins

A

Post-transcriptional mechanisms

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46
Q

A phase where DNA duplication occurs

  • occur with extreme accuracy
  • every nucleotide in the genome must be copied once
A

S phase

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47
Q

Where DNA replication in eukaryotic cell begins

A

Origins of Replication

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48
Q

unwinds the double
helix

A

DNA helicase

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49
Q

replication machinery moves outward from the origin at two replication forks

A

Elongation phase

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50
Q

two distince steps of Inititaion of DNA initiation

A
  • Only in Late mitosis or Early G1
  • S phase
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51
Q

two inactive DNA helicases

A

Mcm helicases

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52
Q

___ → licensing of
replication origins

A

preRC (prereplicative complex)

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53
Q

DNA helicase are activated →DNA unwinding and initiation of DNA synthesis

A

S phase

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54
Q

stimulate a large increase in the synthesis of the four histone subunits that form the histone octamers

A

S-Cdks

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55
Q

helps to control gene expression

A

Chromatin packaging

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56
Q

the chromatin that is highly condensed

A

Heterochromatin

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57
Q

a chromatin that has more open structure

A

Eurochromatin

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58
Q

where cohesin of sister-chromatid depends

A

Cohesin

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59
Q

two subunits of cohesin

A

SMC proteins

60
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.
  • promotes breakdown of nuclear envelope
A

M-Cdk

61
Q

required for the normal assembly of a bipolar mitotic spindle

A

Polo-like kinase (Plk)

62
Q

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

A

Aurora kinases-A

63
Q

controls attachment of sister chromatids to the spindle

A

Aurora kinases-B

64
Q

How does M-Cdk activation begins?

A

Accumulation of M-cyclin

65
Q

Activatation of ____ , removes inhibitory phosphatase that restrain M-Cdk

A

Cdc25

66
Q

Activator of M-Cdk

A

Cdc5

67
Q

Inhibitor of M-Cdk

A

Wee1

68
Q

chromatids are compacted

A

Chromosome condensation

69
Q

two sisters are resolved into distinct, separable units

A

Sister-chromatid resolution

70
Q

Where condensation and resolution of sister-chromatic depends

  • A five-subunit protein complex
A

Condensin

71
Q

depends on mitotic spindle

A

Chromosome segregation

72
Q

overlapped with the plus ends of microtubules from the other pole

A

Interpolar microtubules

73
Q

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

A

Kinetochore microtubules

74
Q

radiate outward from the poles and contact cell cortex

A

Astral microtubules

75
Q

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

A

Centrosome

76
Q

coiled-coil proteins that link the motors to the centrosome, structural proteins, and components of the cell-cycle control system

A

Microtubule-dependent motor proteins

77
Q

move toward the plus ends
- slide the two antiparallelmicrotubules past each other toward the spindle poles, pushing the poles apart

A

Kinesin 5

78
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

79
Q
  • chromokinesins
  • plus-end directed motors that associate with chromosome arms and push the attached chromosome away from the pole
A

Kinesi-4/10

80
Q

minus-end directed motors; motors pull the spindle poles toward the cell cortex and away from each other

A

Dynein

81
Q

helps initiate centrosome duplication

A

G1/S-Cdk

82
Q

M-Cdk phosphorylates several subunits of the nuclear pore complexes

A

Nuclear-envelope breakdown

83
Q

catastrophe or rescue

A

Microtubule dynamic instability

84
Q

promote stability and
catastrophe factors that destabilize microtubule plus ends

A

Microtubule-associated proteins (MAPs)

85
Q

____ play an active part in spindle formation – by creating a local environment that favors both microtubule nucleation and microtubule stabilization

A

Chromosomes

86
Q

bound to the chromatin → activated Ran-GTP – releases microtubule-stabilizing proteins → nucleation and stabilization of microtubules around chromosomes

A

GEF

87
Q

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

A

Kinetochore

88
Q

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

A

Ndc80

89
Q
  • microtubules in the vicinity of the chromosomes become embedded in the plus end-binding sites of the kinetochore. Polymerization at these plus ends then results in growth of the microtubules away from the kinetochore
A

Absence of chromosome

90
Q

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

A

Bi-orientation

91
Q

corrected by a system of trial and error

A

incorrect attachments

92
Q

how does the kinetochore sense a correct attachment?

A

tension

93
Q

securin binds to and inhibits the activity of a protease called _____

A

separase

94
Q

unattached kinetochore acts like an enzyme that catalyzes a change in the conformation of Mad2 → can bind and inhibit Cdc20–APC/C

A

Mad2

95
Q

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

A

chromosome segregation

96
Q
  • initial poleward movement of the chromosomes
A

Anaphase A

97
Q

separation of the spindle poles themselves

A

Anaphase B

98
Q

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

A

Telophase

99
Q

disassembly of ____ ____→ reformation of the nuclear envelope

A

mitotic spindle

100
Q

promotes spindle assembly, chromosome condensation, and nuclear envelope breakdown

A

Phosphorylation by M-Cdk

101
Q

division of the cytoplasm in two

A

Cytokinesis

102
Q

Cytokinesis begins in an animal cell with the appearance of

A

Cleavage furrow

103
Q

The structure underlying this process in cleavage furrow

A

Contractile ring

104
Q

local formation of actin filaments depends on

A

Formin

105
Q

parallel arrays of linear, unbranched actin filaments

A

Formin

106
Q

persists as a tether between the two daughter cells and contains the remains of the central spindle

A

Midbody

107
Q
  • small GTPase of the Ras superfamily
  • controls the assembly and function of the contractile ring at the site of cleavage
A

RhoA

108
Q

How does the mitotic spindle specify the site of division?

A

1st : Astral stimulation model
2nd: Central spindle stimulation model
3rd: Astral relaxation model

109
Q

astral microtubules carry furrow-inducing
signals

A

Astral stimulation model

110
Q

the spindle midzone, or central spindle, generates a furrow-inducing signal that specifies the site of furrow formation at the cell cortex

A

Central spindle stimulation model

111
Q
  • the astral microtubules promote the local relaxation of actin–myosin bundles at the cell cortex
  • cortical relaxation is minimal at the spindle equator; promoting cortical contraction
A

Astral relaxation model

112
Q

in central spindle stimulation model… the ____ ____, or _____ ____, generates a furrow-inducing signal that specifies the site of furrow formation at the cell cortex

A

spindle midzone
central spindle

113
Q

higher-plant cells are enclosed by a semirigid

A

Cell wall

114
Q

the cytoplasm of the plant cell is _____ from the inside out

A

partitioned

115
Q

a new cell wall in plant

A

Cell wall

116
Q

a structure that guide the assemply of cell plate during late anaphase

A

Phragmoplast

117
Q

are usually present in large enough numbers; double once each cycle

A

Mitochondria and Chloroplasts

118
Q

is cut into two during cytokinesis

A

ER

119
Q

is reorganized and fragmented during mitosis

A

Golgi apparatus

120
Q

A cell in which multiple nuclei share the same cytoplasm is called a

A

Syncytium

121
Q

membranes are created around each nucleus in one round of coordinated cytokinesis

A

Cellularization

122
Q

the genomes of two parents mix to generate offspring that are genetically distinct from either parent

A

Meiosis

123
Q
  • contain two slightly different copies, or homologs, of each chromosome, one from each parent
A

Diploids

124
Q

carrying only a single copy of each chromosome → gametes

A

haploid

125
Q

formed during the fusing of sperm and egg fuse

A

Zygote

126
Q

Unique to meiosis, of segregating the homologs

A

Meiosis I

127
Q

no further DNA replication; the sister chromatids pulled apart and segregated

A

Meiosis II

128
Q

duplicated paternal and maternal homologs pair up alongside each other

A

Pair of homologs

129
Q

prolonged period; homologs begin pairing

A

Meiotic prophase

130
Q

interactions between pairing sites

A

Pairing

131
Q
  • four-chromatid structure
A

Bivalent

132
Q

homolog pairs are then locked together by ____ ____

A

homologous recombination

133
Q

the DNA of a chromatid crosses over to become continuous with the DNA of a homologous chromatid

A

Crossovers

134
Q

The paired homologs are brought into close juxtaposition, with their structural axes (___ ___)

A

Axial cores

135
Q

Bridges the gap
- created by closely packed of transverse filaments

A

Synaptonemal complex

136
Q

The five sequential stages of Meiotic prophase

A

Leptotene
Zygotene
Pachytene
Diplotene
Diakinesis

137
Q

homologs condense and pair and genetic recombination begins

A

Leptotene

138
Q

synaptonemal complex begins to assemble at sites where the homologs are closely associated and recombination events are occurring

A

Zygotene

139
Q

assembly process is complete, and the homologs are synapsed along their entire lengths

A

Pachytene

140
Q

disassembly of the synaptonemal complexes and the concomitant condensation and shortening of the chromosomes

A

Diplotene

141
Q

segregation of homologs

A

Diakinesis

142
Q

inter-homolog
connections

A

chiasmata

143
Q

Three features of meiosis that distinguishes it from mitosis

A
  1. Both sister kinetochores in a homolot must attach stably to the same spindle pole
  2. Crossovers
  3. Cohesion is removed in anaphase I
144
Q

cohesins near the centromeres are protected from separase in meiosis I by a kinetochore-associated protein called

A

Shugoshin

145
Q

Functions of crossing-over

A
  • helps hold homologs together
  • Contributes to genetic diversification
146
Q

when homologs fail to separate; some of the resulting haploid gametes lack a particular chromosome, while others have more than one copy of it

A

Nondisjunction

BIO 107 - Cell and Mol. Bio (10 decks)

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