Cell cycle Flashcards
1
Q
stage where DNA synthesis occur
A
S phase
2
Q
Stage where mitosis and cytokineses takes place
A
M phase
3
Q
between M phase and S phase
A
G1 phase
4
Q
between S phase and mitosis.
A
G2 phase
5
Q
Sequential phases that creates Interphase
A
G1, S, G2
6
Q
Cell growth occurs throughout the cell cycle, except during ___
A
Mitosis
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
8
Q
Specialized resting state
A
G0
9
Q
biochemical dissection of cell-cycle control mechanisms
A
Xenopus laevis (Italicized)
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)
11
Q
Several organisms used in the analysis of eukaryotic cell cycle
A
- The budding yeast Saccharomyces cerevisiae
- fission yeast Schizosaccharomyces pombe
12
Q
thymidine analogs that incorporated DNA of dividing cells during the S-phase
A
BrdU (Bromodeoxyuridine)
13
Q
allows the rapid and automatic analysis of large numbers of cells
A
Flow cytometer
14
Q
operates much like a timer that triggers the events of the cell cycle in a set sequence
A
Cell-cycle control system
15
Q
(on/off ) and launch events in a complete, irreversible fashion
A
Binary
16
Q
Three regulatory transitions
A
- Start in late G1
- G2/M transition
- Metaphase-to-Anaphase transition
17
Q
cell commits to cell-cycle entry and chromosome duplication
A
Start (restriction point) in late G1
18
Q
triggers the early mitotic events that lead to chromosome alignment on the mitotic spindle in metaphase
A
G2/M transition
19
Q
stimulates sister-chromatid separation; completion of mitosis and cytokinesis
A
Metaphase-to-anaphase
20
Q
central components of cell-cycle control system
A
Cyclin-dependents kinases (Cdks)
21
Q
are controlled by cyclins
A
Cdks
22
Q
Four classes of cyclins
A
- G1/S-cyclin
- S-cyclins
- M-cyclins
- G1-cyclins
23
Q
activate Cdks in late G1
A
G1/S-cyclin
24
Q
bind Cdks soon after progression through Start and help stimulate chromosome duplication
A
S-cyclins
25
activate Cdks that stimulate entry to mitosis at the G2/M transition
M-cyclins
26
govern the activities of the G1/S-cyclins
G1-cyclins
27
How many Cdks in vertebrates
Four Cdks
28
four Cdks in Vertebrates
- two – G1-cyclins
- one – G1/S- and S-cyclins
- one – S- and M-cyclins
29
active site in the Cdk protein is partly obscured by a protein loop
Absence of cyclin
30
causes the loop to move away from the active site, resulting in partial activation of the Cdk enzyme
Cyclin binding
31
a separate kinase, the Cdk-activating kinase (CAK), phosphorylates an amino acid near the entrance of the Cdk active site
Full activation
32
What happens when Cdk protein is partially obscured by a protein loop
Absense of cyclin
33
When the loop moved away from the active site, what will happen to Cdk?
Partial activation of Cdk enzyme
34
phosphorylates an amino acid near the entrance of the Cdk active site
Cdk-activating kinase (CAK)
35
a protein kinase that inhibits Cdk activity
Wee1 protein kinase
36
a phosphatases that dephosphorylates the site, increasing Cdk activity
Cdc25 phosphatases
37
inactivated cyclin-Cdk complexes
Cdk inhibitor proteins (CKIs)
38
The key regulator that Triggers the Metaphase-to-Anaphase Transition
- a member of the ubiquitin ligase family of enzymes.
Anaphase-promoting complex/Cyclosome (APC/C)
39
protect the protein linkages that hold sister-chromatid pairs together in early mitosis; destroyed at metaphase
Securin
40
destruction inactivates
most Cdks in the cell; proteins are dephosphorylated
S- and M-cyclins
41
ubiquitin ligase; ubiquitylate CKI proteins in late G1; destruction of G1/S-cyclins in early S phase
SCF
42
- increases in mid-mitosis and remains high through G1
- changes in its association
with an activating subunit
APC/C activity
43
APC/C activity depends on what subunits?
- Cdc20 or Cdh1
44
substrate-binding subunits called F-box proteins; constant during cell cycle
SCF activity
45
in early animal embryos – cell-cycle depends exclusively on ____ _____ that involve the regulation of Cdks and ubiquitin ligases and their target proteins
Post-transcriptional mechanisms
46
A phase where DNA duplication occurs
* occur with extreme accuracy
* every nucleotide in the genome must be copied once
S phase
47
Where DNA replication in eukaryotic cell begins
Origins of Replication
48
unwinds the double
helix
DNA helicase
49
replication machinery moves outward from the origin at two replication forks
Elongation phase
50
two distince steps of Inititaion of DNA initiation
- Only in Late mitosis or Early G1
- S phase
51
two inactive DNA helicases
Mcm helicases
52
___ → licensing of
replication origins
preRC (prereplicative complex)
53
DNA helicase are activated →DNA unwinding and initiation of DNA synthesis
S phase
54
stimulate a large increase in the synthesis of the four histone subunits that form the histone octamers
S-Cdks
55
helps to control gene expression
Chromatin packaging
56
the chromatin that is highly condensed
Heterochromatin
57
a chromatin that has more open structure
Eurochromatin
58
where cohesin of sister-chromatid depends
Cohesin
59
two subunits of cohesin
SMC proteins
60
- 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
M-Cdk
61
required for the normal assembly of a bipolar mitotic spindle
Polo-like kinase (Plk)
62
helps control proteins that govern the assembly and stability of the spindle
Aurora kinases-A
63
controls attachment of sister chromatids to the spindle
Aurora kinases-B
64
How does M-Cdk activation begins?
Accumulation of M-cyclin
65
Activatation of ____ , removes inhibitory phosphatase that restrain M-Cdk
Cdc25
66
Activator of M-Cdk
Cdc5
67
Inhibitor of M-Cdk
Wee1
68
chromatids are compacted
Chromosome condensation
69
two sisters are resolved into distinct, separable units
Sister-chromatid resolution
70
Where condensation and resolution of sister-chromatic depends
- A five-subunit protein complex
Condensin
71
depends on mitotic spindle
Chromosome segregation
72
overlapped with the plus ends of microtubules from the other pole
Interpolar microtubules
73
attached to sister-chromatid pairs at large protein structures called kinetochores
Kinetochore microtubules
74
radiate outward from the poles and contact cell cortex
Astral microtubules
75
consists of a cloud of pericentriolar matrix that surrounds a pair of
centrioles
Centrosome
76
coiled-coil proteins that link the motors to the centrosome, structural proteins, and components of the cell-cycle control system
Microtubule-dependent motor proteins
77
move toward the plus ends
- slide the two antiparallelmicrotubules past each other toward the spindle poles, pushing the poles apart
Kinesin 5
78
- are minus-end directed motors
- cross-link antiparallel interpolar microtubules at the spindle midzone and tend to pull the poles together
Kinesin-14
79
- chromokinesins
- plus-end directed motors that associate with chromosome arms and push the attached chromosome away from the pole
Kinesi-4/10
80
minus-end directed motors; motors pull the spindle poles toward the cell cortex and away from each other
Dynein
81
helps initiate centrosome duplication
G1/S-Cdk
82
M-Cdk phosphorylates several subunits of the nuclear pore complexes
Nuclear-envelope breakdown
83
catastrophe or rescue
Microtubule dynamic instability
84
promote stability and
catastrophe factors that destabilize microtubule plus ends
Microtubule-associated proteins (MAPs)
85
____ play an active part in spindle formation – by creating a local environment that favors both microtubule nucleation and microtubule stabilization
Chromosomes
86
bound to the chromatin → activated Ran-GTP – releases microtubule-stabilizing proteins → nucleation and stabilization of microtubules around chromosomes
GEF
87
a giant, multilayered
protein structure that is built at the centromeric region of the chromatid
Kinetochore
88
rod-shaped protein complex; linking the microtubule to the kinetochore
Ndc80
89
- 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
Absence of chromosome
90
sister chromatids in a pair attach to opposite poles of the mitotic spindle
Bi-orientation
91
corrected by a system of trial and error
incorrect attachments
92
how does the kinetochore sense a correct attachment?
tension
93
securin binds to and inhibits the activity of a protease called _____
separase
94
unattached kinetochore acts like an enzyme that catalyzes a change in the conformation of Mad2 → can bind and inhibit Cdc20–APC/C
Mad2
95
sudden loss of sister-chromatid cohesion at the onset of anaphase → _____ _____
chromosome segregation
96
- initial poleward movement of the chromosomes
Anaphase A
97
separation of the spindle poles themselves
Anaphase B
98
the two sets of chromosomes are packaged into a pair of daughter nuclei
Telophase
99
disassembly of ____ ____→ reformation of the nuclear envelope
mitotic spindle
100
promotes spindle assembly, chromosome condensation, and nuclear envelope breakdown
Phosphorylation by M-Cdk
101
division of the cytoplasm in two
Cytokinesis
102
Cytokinesis begins in an animal cell with the appearance of
Cleavage furrow
103
The structure underlying this process in cleavage furrow
Contractile ring
104
local formation of actin filaments depends on
Formin
105
parallel arrays of linear, unbranched actin filaments
Formin
106
persists as a tether between the two daughter cells and contains the remains of the central spindle
Midbody
107
- small GTPase of the Ras superfamily
- controls the assembly and function of the contractile ring at the site of cleavage
RhoA
108
How does the mitotic spindle specify the site of division?
1st : Astral stimulation model
2nd: Central spindle stimulation model
3rd: Astral relaxation model
109
astral microtubules carry furrow-inducing
signals
Astral stimulation model
110
the spindle midzone, or central spindle, generates a furrow-inducing signal that specifies the site of furrow formation at the cell cortex
Central spindle stimulation model
111
- 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
Astral relaxation model
112
in central spindle stimulation model... the ____ ____, or _____ ____, generates a furrow-inducing signal that specifies the site of furrow formation at the cell cortex
spindle midzone
central spindle
113
higher-plant cells are enclosed by a semirigid
Cell wall
114
the cytoplasm of the plant cell is _____ from the inside out
partitioned
115
a new cell wall in plant
Cell wall
116
a structure that guide the assemply of cell plate during late anaphase
Phragmoplast
117
are usually present in large enough numbers; double once each cycle
Mitochondria and Chloroplasts
118
is cut into two during cytokinesis
ER
119
is reorganized and fragmented during mitosis
Golgi apparatus
120
A cell in which multiple nuclei share the same cytoplasm is called a
Syncytium
121
membranes are created around each nucleus in one round of coordinated cytokinesis
Cellularization
122
the genomes of two parents mix to generate offspring that are genetically distinct from either parent
Meiosis
123
- contain two slightly different copies, or homologs, of each chromosome, one from each parent
Diploids
124
carrying only a single copy of each chromosome → gametes
haploid
125
formed during the fusing of sperm and egg fuse
Zygote
126
Unique to meiosis, of segregating the homologs
Meiosis I
127
no further DNA replication; the sister chromatids pulled apart and segregated
Meiosis II
128
duplicated paternal and maternal homologs pair up alongside each other
Pair of homologs
129
prolonged period; homologs begin pairing
Meiotic prophase
130
interactions between pairing sites
Pairing
131
- four-chromatid structure
Bivalent
132
homolog pairs are then locked together by ____ ____
homologous recombination
133
the DNA of a chromatid crosses over to become continuous with the DNA of a homologous chromatid
Crossovers
134
The paired homologs are brought into close juxtaposition, with their structural axes (___ ___)
Axial cores
135
Bridges the gap
- created by closely packed of transverse filaments
Synaptonemal complex
136
The five sequential stages of Meiotic prophase
Leptotene
Zygotene
Pachytene
Diplotene
Diakinesis
137
homologs condense and pair and genetic recombination begins
Leptotene
138
synaptonemal complex begins to assemble at sites where the homologs are closely associated and recombination events are occurring
Zygotene
139
assembly process is complete, and the homologs are synapsed along their entire lengths
Pachytene
140
disassembly of the synaptonemal complexes and the concomitant condensation and shortening of the chromosomes
Diplotene
141
segregation of homologs
Diakinesis
142
inter-homolog
connections
chiasmata
143
Three features of meiosis that distinguishes it from mitosis
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
cohesins near the centromeres are protected from separase in meiosis I by a kinetochore-associated protein called
Shugoshin
145
Functions of crossing-over
- helps hold homologs together
- Contributes to genetic diversification
146
when homologs fail to separate; some of the resulting haploid gametes lack a particular chromosome, while others have more than one copy of it
Nondisjunction
