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CBG PANT Replication, transcription and translation > CBG Lecture 9: Cell Cycle > Flashcards

CBG Lecture 9: Cell Cycle Flashcards

(85 cards)

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1
Q

what is the cell cycle

A

a four phase internal clock in the cell that regulates cell division

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2
Q

which domain is it found in

A

eukaryotes

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3
Q

what are the four phases of the cell cycle

A 
INTERPHASE:
G1 - growth
S: Synthesis
G2: growth and prep for division
MITOSIS/MEIOSIS + CYTOKINESIS
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4
Q

what stages does interphase include

A

growth G1
synthesis
growth and prep for division G2

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5
Q

how long does G1 phase last

A

8 hours

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6
Q

how long does synthesis phase last?

A

DNA replication lasts c.12 hours

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7
Q

what happens ni synthesis phase

A

dna replication

eg. diploid to tetraploid

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8
Q

which phase is the longest in the cell cycle

A

synthesis: c.12 hours

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9
Q

what happens in G2 phase

A

growth and prep for cell division c. four hours

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10
Q

what happens in M phase

A

meiosis/mitosis/cytokinesis

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11
Q

how long does M phase last

A

half hour

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12
Q

what evidence exists for M phase

A

its histologically obvious - chromosomes condense

can see stages of meiosis and mitosis

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13
Q

what evidence is there for S phase

A

identify by 3H- thymidine autoradiography

50% of cells normally labelled, shows cells spend 50^ of their time in S phase

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14
Q

how can G1 and G2 phases be identified

A

use flourescent dyes to measure [DNA]

use flow cytometry

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15
Q

what is flow cytometry

A

each drip from vibrating nosel adds just a single cell, so if you add a flourescent dye, can tell which phase youre in by amount of flourescence

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16
Q

what is flow cytometry used for

A

measures [DNA] can see which phase of cycle a cell is in

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17
Q

which colour flourescence do cells in G2 phase show in flow cytometry

A

green

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18
Q

compare the amount of flourescence in G1 cells to G2

A

G2 has double amount of DNA than G1 therefore will have double the flourescence

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19
Q

which cells are used for fusion experiments

A

HeLa cells

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20
Q

what are HeLa cells

A

cervical cancer cells - immortal cells

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21
Q

what was the main result from fusion experiments

A

S phase nuclei induce S phase in G1 but not in G2

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22
Q

what is the result of a fusion experiment with a cell in S phase and a cell in G1 phase?

A

S contains factors that drive G1 to replicate DNA so get 2 S phase cells

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23
Q

what is the result of a fusion experiment with a cell in S phase and a cell in G2 phase?

A

G2 are refractory to the S phase factors, so no change to cells

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24
Q

what is the result of a fusion experiment with a cell in G2 phase and a cell in G1 phase?

A

no change

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25
what did injection studies in frog oocytes show
maturation promoting factor can induce M phase in G2 nuclei
26
what does maturation promoting factor do
induce M phase in G2 nuclei
27
if you have a G2 cell and place in external control progesterone into it, what happens
induces M phase
28
how can M phase be induced
by adding progesterone
29
what does microinjection of M phase cytoplasm into G2 cells do
induces M phase
30
what can cell division cycle mutants do
help to understand cell cycle regulation
31
what are checkpoints in a cell cycle
restricition point in mammalian cell/start point in yeast where Cdc21/ Cdk1 all work
32
what happens to the cell cycle of yeast mutants
temperature sensitive yeast mutants arrect in G1 at high T
33
what is human homologue of Cdc28
Cdk1
34
what phase do temperature sensitive yeast mutants go to at high temperatures
G1 go to G0 at high temperatures
35
what are CDC mutants? what does CDC stand for
cell division cycle mutants Cdc28
36
what does Cdk stand for | what can an arrest to Cdk1 do
cyclin dependent kinase | Cdk1 can cause arrest to G1 phase
37
what are check points in a cell cycle regulated by
internal and external factors
38
how many check points in the cell cycle are there | what are they
3 G1 G2/M Metaphase
39
what internal/external growth factors taken into account at G1 checkpoint
internal growth factors: cell size | external growth factors: growth hormones, hormone factors, check whether DNA is damaged
40
what internal/external growth factors taken into account at G2/M checkpoint
internal: check all DNA present (can arrest at this point+wait/grow DNA) is all DNA replicated cell size dna damage
41
what internal/external growth factors taken into account at metaphase checkpoint
chromosome alignment
42
how do you rectify misaligned chromosomes in metaphase checkpoint
use tubulin cytoskeleton
43
what are cyclins
proteins that cycle in concentration over the cell cycle
44
give an example of an S-type cyclin
cyclin D - which cycles in sea urchin embryos
45
how does [S-type cyclin] change over time
levels build up from G1 through to S through to G2 and drop dramatically at G2/M checkpoint
46
what is progress through the cell cycle controlled by
a cyclin dependent kinase
47
whatt do cyclins do
detrermine the specificity of the CDK for its protein targets
48
how many CDKs do yeast have, what?
yeast have a single CDK, vertebrates have several
49
what can misregulation of CDKs result in
uncontrolled growth - cancer
50
what are CDKs given specificity by
cyclins
51
why wont CDKs work alone
cyclins tell CDKs what they should be modifying and which proteins they should switch on/off enzymes to activate etc
52
what is the passage through metaphase checkpoint associated with
the destruction of M cyclin by APC: anaphase promoting complex
53
what is APC - what does it do
anaphase promoting complex | associated with the destruction of M cyclin
54
what complex promotes passage through start/G1 checkpoints
CDK+ G1 cyclin | and CDK+G1/S cyclin
55
how does first complex promote passage through start/G1 checkpoints
CDK+ G1 cyclin and CDK+G1/S cyclin oassage through start by phosphorylating eg. Retinoblastoma protein which frees EF2 - transcription factor
56
give an example of passage through start checkpoint of cell cycle
CDK + G1/S cyclin | retinoblastoma protein which frees EF2
57
how do CDKs become activated
association with a cyclin makes it partly active | phosphorylation by CAK makes it fully active
58
how does a CDK become partial active
association with cyclin
59
how does a CDK become fully active
after association with cyclin, becomes phosphorylated by Cak
60
how can CDK be both inactivated AND activated by phosphorylation
has multiple phosphorylation binding sites
61
how is CDK inactivated
phosphorylation of 2 phosphate groups by Wee1
62
How does CDK+S cyclin complex initiate synthesis
phosphorylation
63
give an example of CDK+S cyclin complex initiating synthesis
histone mRNA stem-loop binding protein-stabilises histone mRNA
64
how is DNA synthesis initiated
by CDK+S cyclin being phosphorulated
65
what promotes passage through G2/M checkpoint
by CDK+M cyclin (maturation promoting factor)
66
what is MPF made of
maturation promoting factor | CDK+M cyclin
67
how is passage through G2/M checkpoint promoted
MPF (CDK+MCyclin) phosphrylation eg. nuclear lamins - break down nucleus myosin - prevent cytokinesis condensin = condenses chromosomes
68
what happens when cyclin synthesis>degradation
cyclin accumulates and can force cyclin CDK complex to go throughcheckpoint
69
how is a CDK/cyclin complex broken down
cyclin ubiquitination by APC -anaphase promoting complex - and degraded cyclin degraded, CDK is recycled
70
how are cyclins regulated
by a balance of synthesis and degradation
71
what pathway is used to regulate cyclins
MAPKinase/K/K patheay which results in G1 cyclin expression
72
which pathway results in G1 cyclin expression
MAPK/K/K Growth factor cascade
73
what are CDK/cyclin complexes inhibited by
Cdk inhibitor proteins (CKIs) like p21
74
what is a CKI
Cdk inhibitor protein
75
name a CKI
p21
76
what is p21
a CDK inhibitor protein
77
how can a mutation be detected
p53 presence
78
what can a mutation in p53 and p21 do
more likely to replicate damaged/mutated DNA -> lead to cancer
79
name some tumour suppressor genes
p21 | p53
80
what is a tumour suppressor gene
gene that encode proteins that act as brakes on cell cycle
81
what type of mutation does a tumour supressor gene need to become dangerous
recessive mutation - both copies need to be broken
82
give ecamples of tumour supressor genes
genes encoding p53 | retinoblastoma protein
83
what is an oncogene
gene that if a dominant mutation exists, it will accelerate cell cycle progression
84
give ecample of oncogene
genes encoding Ras, RTKs,Myc
85
how is an oncogene mutation dangerous
it generates the genes to be constituently on regardless of promoters/operatiors/repressors

CBG PANT Replication, transcription and translation (10 decks)

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