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BIO230 Section 2 > 2.10: The Cell Cycle > Flashcards

2.10: The Cell Cycle Flashcards

1
Q

does DNA replication occur in mitosis

A

NO, before

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2
Q

which two processes are included in M phase

A

mitosis and cytokinesis

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3
Q

which are the transition to enter mitosis and which questions are asked

A

G2/M transition
is all DNA replicated? is the environment favorable?

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4
Q

state the purpose of cell cycle checkpoints

A

ensure conditions are suitable for division

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5
Q

which are the transition to trigger anaphase and proceed to cytokinesis and which questions are asked

A

metaphase to anaphase transition. are all chromosomes attached to the spindle?

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6
Q

which are the transition to enter cell cycle and proceed to S phase and which questions are asked

A

start transition. is the environment favorable

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7
Q

at a molecular level, what are checkpoints mediated

A

the controlled activity of cyclin dependent kinases (Cdks)

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8
Q

what do Cdks do and what do they require

A

Cdks phosphorylate targets proteins for the cell cycle to progress, Cdks require cyclins to be active

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9
Q

t/f Cdks and cyclins can be present throughout all cell cycle stages

A

false. Cdks can, cyclins are made and broken down at different cell cycle stages

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10
Q

the cyclin-cdk combo controls what

A

which target proteins are phosphorylated

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11
Q

S cdk phosphorylates ? at ? stage of the cell cycle

A

S cdk phosphorylates dna helicases at G1 to S stage of the cell cycle

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12
Q

which cdk complex is is at the start of the cell cycle

A

G1/S cdk w G1/S cyclin

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13
Q

Mcdk phosphorylates ? at ? stage of the cell cycle

A

phosphorylates lamin (nuclear envelope breakdown) and microtubule associated proteins (spindle assembly) it is in between the G2 and M

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14
Q

t/f one cdk may work with multiple cyclines, but cyclins only work one stage (can be the same cdk, must be a different cyclin)

A

true

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15
Q

for budding yeast, what are the cdk partner(s)
for vertebrates, what are the cdk partner(s)

A

yeast: cdk1. vertebrates: cdk2

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16
Q

cyclins can be ubiquitinated, polyubiquitination marks cyclins for ________ by the _________

A

cyclins can be ubiquitinated, polyubiquitination marks cyclins for degradation by the proteasome

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17
Q

if cyclins are broken down, cdks will still/no longer be active

A

no longer

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18
Q

t/f if cyclins are degraded, cdks are spared

A

yes

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19
Q

______ & _______ promote M-cyclin degradation

A

APC/C and Cdc20

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20
Q

APC/C and Cdc20 act as an ?

A

E3 ubiquitin ligase

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21
Q

which processes determines which cyclin-cdk complex is active at any time

A

synthesis and degradation

22
Q

cdks are activated by which enzyme

A

cdk activating kinase (CAK)

23
Q

cyclin is absolute required for cdk activity by exposing the _____, once it is exposed, cak can phosphorylate cdk to further activate it

A

t loop

24
Q

which enzyme reverse the effects of cyclin cdks by removing phosphorylation from proteins

A

protein phosphatases (PP2As)

25
Q

t/f pp2as usually have the same targets as cyclin-cdks

A

true - pp2a and m-cdk participate in a complex feedback loop

26
Q

m-cdk and pp2a compete for the same targets, compare what happens before M phase and what happens during M phase

A

Before M-phase
-PP2A is active
-PP2A dephosphorylates
- M-Cdk targets to stop progression into mitosis
During M-phase
-M-cyclin is produced
-M-Cdk is active
-M-Cdk indirectly inhibits PP2A activity
- M-cyclin phosphorylates its targets to promote mitosis progression

27
Q

cdk inhibitor proteins (ckis) bind cyclin-cdks and 2 examples

A

ckis disrupt the cyclin-cdk interaction, which inactivates the cdk (cki like a clamp to block active site and distort atp binding site)
examples: p27, p21

28
Q

t/f the inhibitory phosphorylation is at a different site from the activating phosphate added by cak

A

true

29
Q

what are the functions of wee1 kinase, cdc25 phosphatase

A

wee1 kinase: adds inhibitory phosphorylation
cdc25 phosphatase: can remove the inhibitory phosphorylation

30
Q

which two enzymes have opposite effects in regards to cyclin cdks

A

wee1 kinase (inhibits) vs cdc25 phosphatase (removes the inhibitory phosphorylation = activates)

31
Q

Cdc25 phosphatase can remove the inhibitory phosphorylation on M-Cdk and must be phosphorylated/dephosphorylated to be active

A

phosphorylated

32
Q

positive/negative feedback loops ensure robust cyclin cdk activation

A

positive

33
Q

name an example of active m-cdk activates its activators

A

cdc25 phosphorylation

34
Q

name 2 examples of active m-cdk inhibiting its inhibitors

A
  • pp2a phosphatase inactivation
  • wee1 kinase phosphorylation
35
Q

describe wee1 phosphorylation and what is it an example of

A

its an example of active m-cdk inhibiting its inhibitors. wee1 phosphorylation = inactive = more inhibitory phosphate = more active m-cdk (+ feedback)

36
Q

what type of feedback creates an all or nothing choice to proceed

A

positive feedback

37
Q

How many of the following statements about the cell cycle are TRUE?
* During cell growth, all molecules in the cell are produced together over
the same time period.
* Different cell cycle stages can be directed by the same Cdks.
* Different cell cycle stages can be directed by the same Cyclins.
* Active and inactive Cdks can have a phosphate group at the Cdk-
activating kinase phosphorylation site.
a) 1
b) 2
c) 3
d) 4

A

B.
statement 1 is wrong bc you can make and degrade diff cyclins. statement 4 is wrong bc of inhibitory

38
Q

what are examples of molecular inputs that regulate cyclin-cdk activity

A

mitogens/growth factors

39
Q

____ is transcription factor req for s-phase gene expression

A

e2f

40
Q

___ binds and inhibits E2F, this can be inhibited by phosphorylation which allows e2f to continue

A

rb

41
Q

mitogens trigger production of the cell cycle control protein ____

A

myc

42
Q

are mitogens ec or ir signaling molecules

A

ec

43
Q

mitogens activate a signalling pathways including: ? (3)

A

rtk, ras, map kinase cascade

44
Q

activation of rtk, ras, map kinase cascade leads to upregulation expression of ____

A

myc

45
Q

myc is a key TF involved in _________ control

A

cell cycle

46
Q

explain how myc activates g1-cdk which inhibit rb

A
  1. Myc activates G1-cyclin gene expression
  2. G1-Cdk phosphorylates Rb
  3. Phosphorylated Rb releases E2F
  4. E2F activates expression of S-phase genes
47
Q

list 2 examples of positive feedback regarding myc activation

A
  • e2f autoactivation
  • g1/s-cdk and s-cdk phosphorylation of rb
48
Q

dna damage blocks cell cycle progression via _______ and induces ___ TF activation

A

cki synthesis, p53

49
Q

p53 activates ____ expression which is a cki that inhibits g1/s-cdk and s cdk

A

p21

50
Q

what is p21 activation caused by (2 upstream steps)

A

dna damage induces p53 TF activation where p53 activates p21

51
Q

Which of following will mimic the effects of a Cdk inhibitor?
a) Cyclin overexpression
b) p27 downregulation
c) M-cyclin polyubiquitylation
d) Cdc25 phosphatase activity

A

C.
A is wrong bc it’s the green light. B, p27 is a ski, down regulate an inhibitor does the opposite. D, green light that removes inhibiting phosphorylation

BIO230 Section 2 (12 decks)

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