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CSF Block 5 > cell cycle review deck > Flashcards

cell cycle review deck Flashcards

1
Q

part of the cell cycle that contains the commitment point

A

G1

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2
Q

what is the effects of progesterone on dividing cells?

A

progesterone increased levels of MFP, MPF was noted to parallel cyclin B

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3
Q

actions of cyclins on CDKs (2)

A
  • activates CDKs

- directs CDKs to specific targets in the cell

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4
Q

what are the “master regulators” of cell cycle progression?

A

cyclin-CDK complexes

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5
Q

how does MAP kinase relate to the cell cycle?

A

growth factors stimulate Ras, which activates MAP kinase pathway, which results in the stimulation of cyclin D

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6
Q

what stimulates cyclin D?

A

growth factors

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7
Q

what are the cyclin-CDK complexes in G1?

A

cyclin D-CDK4/6

cyclin E-CDK2

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8
Q

when is the restriction point in G1?

A

between cyclin D-CDK4/6 and cyclin E-CDK2

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9
Q

what is the cyclin-CDK complex in s?

A

cyclin A-CDK2

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10
Q

what are then cyclin-CDK complexes in G2?

A

cyclin A-CDK1

cyclin B- CDK1

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11
Q

how do cyclins activate CDKs?

A
  • cyclin binds to CDK and allows ATP binding and exposure of P site on T loop
  • t loop position change unblocks the active site
  • phosphorylation on T loop by CDK-activating kinase
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12
Q

in G1, what initially activates cyclin d?

A

growth factors

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13
Q

what is the primary role of cyclin D-CDK4/6 complexes?

A

to inactivate Rb protein (tumor suppresor)

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14
Q

what is the role of Rb protein?

A

tumor suppressor that inhibits activity of E2F

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15
Q

what is E2F?

A

transcription factor that controls the expression of DNA replication enzymes cyclins D/E/A

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16
Q

what is established after the activation of E2F?

A

positive feedback loop

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17
Q

what is the definition of “commitment point”?

A

point after which growth factors are no longer required for cell division to proceed

18
Q

what happens at the end of G1?

A

accumulation of cyclin E

19
Q

what CDK does cyclin E bind?

A

CDK2

20
Q

what is the action of cyclin E-CDK2?

A

fully inactivates Rb protein allowing for high levels of E2F to accumulate

21
Q

what are high levels of E2F needed?

A

cyclin A promoter only weakly binds E2F, so high levels are needed

22
Q

what else does the cyclin E-CDK2 complex accomplish?

A

“licenses” cell for replication through sequential assembly of pre-replication complexes (ORC, CDC6, CDT1, MCM helices)

23
Q

what triggers the transition from G1-S phase?

A

cyclin E is degraded and CDK2 is freed to complex with cyclin A

24
Q

what will activate MCM helices and recruit DNA pol?

A

cyclin A-CDK2 and other kinases

25
Q

what happens to CDC6 at the end of S phase?

A

CDC6 is unbiquitinated and degraded

26
Q

what triggers transition from S-G2 phase?

A

accumulation of cyclin A and cyclin B

27
Q

what is another term for MPF?

A

cyclin B-CDK1

28
Q

what controls the activity of cyclin B-CDK1?

A

Wee-1 kinase and CDC25-phosphatase

29
Q

what is the action of Wee-1 kinase?

A

adds phosphate to Y15 to stop the cell from dividing if it is too small

30
Q

what is the action of CDC25-phosphatase?

A

removes the inhibitory phosphate from Y15

31
Q

what is the action of CAK?

A

adds phosphate to T161- which is activating

32
Q

what will trigger mitosis?

A

phosphorylation of specific targets by cyclin B-CDK1 complexes

33
Q

what are some of these “targets”? (3)

A
  • lamin filaments – will breakdown nuclear envelope
  • microtubule assembly proteins- will form mitotic spindle
  • APC/C- see below
34
Q

What is APC/C?

A

“Anaphase promoting complex cyclosome” that is a ubiquitin ligase complex

35
Q

what are the 2 targets of APC/C?

A
  • remove securin from seprase to allow chromosomes to separate in anaphase
  • degrade cyclin B
36
Q

in what situation is continued high levels of cyclin B desired?

A

if cell i destined to be quiescent

37
Q

what controls APC/C?

A

CDH1- targets APC/C to cyclin B

CDC20- targets APC/C to securin

38
Q

during which phase of mitosis does condensation of chromosomes occur?

A

prophase

39
Q

during which phase of mitosis is securin inactivated?

A

once all of the chromosomes have properly aligned, APC/C will remove securin so that seprase can separate sister chromatids

40
Q

during which has of mitosis is the actual separation of sister chromatids?

A

anaphase

CSF Block 5 (18 decks)

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