Chapter 18: The Cell Cycle Flashcards
1
Q
list 3 reasons why cell division is needed
A
- reproduction
- growth
- regeneration
2
Q
unicellular organisms primarily use cell division for
A
reproduction
3
Q
in multicellular organism cell division is important in
A
- growth
- repair of tissues
4
Q
what 4 events must occur for cell division?
A
- reproductive signal
- replication
- segragation
- cytokinesis
5
Q
the reproductive signal is necessary to
A
initiate cell division
6
Q
replication refers to the
A
duplication of chromosomes
7
Q
segregation is the distribution of
A
replicated chromosomes to the 2 daughter cells
8
Q
cytokinesis is the
A
separation of the 2 new cells
9
Q
in prokaryotes binary fission results in
A
2 new cells
10
Q
what are 2 external factors that initiate cell division?
A
- nutrient concentration
- environmental conditions
11
Q
in bacteria what speeds up the division cycle?
A
abundant food supplies
12
Q
in eukaryotic somatic cells each contain a
A
homologous pair of chromosomes
- each parent contributes 1 homolog
13
Q
for mammals all somatic cells possess
A
diploid (2n DNA)
14
Q
germ cells lead to the production of
A
gametes
15
Q
gametes ONLY contain
A
1 set of chromosomes (haploid= 1n)
16
Q
fertilization is when
A
2 haploid gametes fuse
17
Q
fertilization leads to the formation of a
A
diploid zygote (2n)
18
Q
what are the 2 types of cell division in eukaryotes?
A
- mitosis
- meiosis
19
Q
in what cells does mitosis occur?
A
in somatic cells
20
Q
in what cells does meiosis occur?
A
in germ cells
21
Q
mitosis results in
A
2 identical sister cells
22
Q
meiosis produces
A
4 haploid daughter cells different from each other and the parent
23
Q
what are the 4 stages, in order, of the cell cycle?
A
- G1
- S
- G2
- M
24
Q
what are examples of some things that are synthesized in the G2 phase?
A
- signaling molecules
- regulatory proteins
- histone proteins
- tubulin
25
during what stage of the cell cycle does reformation of the nuclear envelope occur?
cytokinesis
26
reformation of the nuclear envelope allows for
uncoiling of the chromosomes
27
what are the stages of mitosis?
- interphase
- prophase
- prometaphase
- metaphase
- anaphase
- telophase -> cytokinesis
28
in early embryonic development cell division occurs but there is little
growth
29
what stage of the cell cycle is skipped during early embryonic development?
G1 & G2
30
without G1 or G2 cells will continue to
decrease in size
31
for budding yeast what is the name of the regulatory check point?
START
32
What factors affect the START check point in yeast?
- nutrient availability
- mating factors
- cell size
33
to maintain a constant size yeast cells must reach a minimum size to
pass START
34
what is the resting state for mammalian cells?
G0
35
what are the 4 cell cycle checkpoints
1. DNA damage (G1)
2. DNA damage (S)
3. DNA damage (G2)
4. spindle assembly (M)
36
the G1 checkpoint checks for
1. cell size
2. nutrients
3. GFs
4. DNA damage
37
checkpoint for DNA damage in G1 is mediated by
p53
38
the S phase checkpoint includes coupling of the
S to G2 and M phase
39
what is the licensing factor of the S phase checkpoint?
MCM helicase
40
MCM helicase can only bind in
G1
41
the S phase checkpoint prevents DNA from being replicated more than once..how is this done?
by preventing the cells in G2 from reentering S phase
42
when does the MCM helicase bind?
in the junction between G1 & S phase
43
the G2 checkpoint of the cell cycle checks for
- cell size
- DNA replication
- DNA damage
44
the checkpoint for DNA damage in G2 is mediated by
Chk1 & Chk2
45
the checkpoint during the M phase checks for
- chromosome attachment to spindle
- chromosome alignment
46
what checkpoint occurs prior to anaphase?
the spindle assembly checkpoint
47
when do the 2 resting states occur during the cell cycle?
1. G1
2. M
48
progression of the cell cycle is regulated through
- kinases
- phosphatases
49
kinases...
phosphorylates proteins
50
phosphatases
dephosphorylates proteins
51
what are the 3 key components of cell cycle regulation?
1. maturation promoting factor (MPF)
2. Cdc
3. Cyclins
52
MPFs were first studied in
frog oocytes
53
in MPFs the transition from G2 to M is mediated by
Cdk1 & cyclin B
54
CDK1 and cyclin B are together known as the
maturation promoting factor (MPF)
55
Cdc was first studied in
yeast
56
cdc stands for
cell division mutants
57
the temperature sensitive mutants were found to undergo ___________ ____________ during specific points in the cell cycle.
growth arrest
58
most Cdcs have been identified as
kinases called cyclin dependent kinases (Cdk)
59
cyclins were discovered in what studies?
sea urchin
60
during the sea urchin studies a series of proteins were identified to display a periodic pattern of
accumulation & degradation
61
complexes of cyclin & Cdk trigger proteins at
checkpoints
62
activation of Cdk-cyclin complexes requires
phosphorylation: kinases
dephosphorylation: phosphatases
63
the Cdk/cyclin complex phosphorylates other ___________ which induces...
- proteins
- progression through the cycle
64
what cdk/cyclin complex corresponds to the G1 phase?
Cdk4,6/CycD
65
what cdk/cyclin complex corresponds to the G1-S phase?
Cdk2/CycE
66
what cdk/cyclin complex corresponds to the S phase?
Cdk2/CycA
67
what cdk/cyclin complex corresponds to the G2 phase?
Cdk1/CycB
68
how are cyclins degraded?
by becoming ubiquitinated
69
which cdk/cyclin complex is responsible for pushing cells past the G1 restriction point?
cdk4,6/cyclinD
70
cdk4,6 is constitutively...
expressed
71
cyclin D is synthesized in the presence of
GFs
72
Rb physically inhibits
E2F
73
E2F is the transcription factor that transcribes the next cyclin known as
cyclin E
74
synthesis of cyclin D activates ___________ which phosphorylates _____. ____________ then promotes the transcription of _______________ ___.
- Cdk4,6
- Rb
- E2F
- cyclin E
75
MCM can only bind in what phase of the cell cycle?
S phase
76
what couples S phase to G2 phase?
Cdk2/cyclin E and MCM
77
activated cdk2/cyclin E phosphorylates and activates
MCM
78
what does MCM do to DNA?
denatures it for replication in the S phase
79
Cdk 1 activation is through the phosphorylation of
threonine-161
80
Cdk1 inhibition is through the phosphorylation of
Tyr15
81
what is the MPF composed of
Cdk1/CyclinB
82
MPF is inactivated by
cyclin B degradation
83
what controls the timing of cell cycle events by inhibitory phosphorylation of Cdks?
wee1 kinases
84
what removes inhibitory phosphates from Cdks?
Cdc25 phosphatase
85
removal of inhibitory phosphates controls the
entry & progression of the cell cycle
86
what are 4 functions of mitotic protein kinases?
1. chromatin condensation
2. nuclear envelope breakdown
3. fragmentation of Golgi
4. spindle formation
87
what are the steps in the progression to anaphase?
MPF -> APC activation -> MPF Ubiquitination -> MPF degradation
88
ubiquitination of securin causes an active ________ that leads to the degradation of ___________.
- separase
- cohesin
89
what is a target of cyclin D/Cdk 4,6 that is often mutated in a wide array of human tumors?
RB
90
Rb is the prototype of a tumor suppressor genes b/c its a gene whose
inactivation leads to tumor development
91
the proteins encoded by tumor suppressor genes act as
brakes slowing down cell cycle progression
92
GF signaling activates what pathway?
the Ras pathway
93
Ras activation uses what cdk/cyclin complex?
Cdk4,6/Cyclin D
94
an active Rb binds E2F transcription factor preventing
- transcription of genes for DNA replication
- passage through G1 into S phase
95
when can Rb not bind to E2F?
when phosphorylated
96
phosphorylated Rb cannot bind to E2F leading to
- activation of gene transcription triggering onset of S phase
97
when DNA damage is detected the cells arrest in _____ which activates _____ & ______these phosphorylate _____.
- G1
- ATM & Chk2
- p53
98
activated p53 causes transcription of ______. This inhibits the activity of _____________. what does this inhibit?
- p21
- Cdk2/cyclin E
inhibits:
- G1 to S transition
- replication
99
in early G1 p27 inhibits
Cdk2/Cyclin E
100
GF signaling causes the
degradation of p27 through phosphorylation
101
in late G1 ___________ gets involved leading to...
- MCM
- DNA replication
102
Chk1 and Chk2 are
inhibitors of cell cycle progression
