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Cell Bio And Disease > Mitosis Phase > Flashcards

Mitosis Phase Flashcards

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1
Q

What is stopped from getting degraded in the spindle assembly checkpoint

A

Cyclin b and securin (allowing anaphase)

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2
Q

Which m cyclin is nuclear and which moves to nucleus from cytoplasm

A

Nuclear is a

Cytoplasmic is b

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3
Q

When does cyclin a get degraded

A

Before prometaphase

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4
Q

When does cyclin b increase / peak and then lower

A

Peak is at prometaphase

Low is met- anaphase

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5
Q

What is the main cdc25 for cdk1 cyclin b activation by removal of wee1/myt1 phos

A

Cdc25b

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6
Q

What kinase is a target of the active cdk1 and cyclin b which causes a positive feedback loop for more activation

A

Polo like kinase

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7
Q

What does plk do in respect to cdk 1 activation

A

Phos of wee and myt inhibiting them

Also phos of cdc25a, and c as well as b which all cause cdk activation

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8
Q

How can cyclin a aswell as main cdc25b be a trigger for mitosis via cdk1 activation

A

When in complex with cdk it allows aurora a activation of plk

Plk then causes a loop via phos of cdc25c

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9
Q

How many centrioles are from centrosomes

A

2

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10
Q

Explain centrosome cycle which duplicates for mitosis

A

In g1 centrosome pulls apart but held by procentrioles

Centrosome is duplicated in s phase

Centrosome disjunction through pulling of procentrioles in s/g2

Full centrosome separation in mitosis and bipolar spindle formation

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11
Q

What is pulling apart of procentrioles called in g2 and what kinase involved

A

Centrosome maturation via plk4

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12
Q

Other than activating cdk1 cyclin b and plk for centrosome maturation, what do plk do

A

Prophase pathway of cohesin ring removal on sister chromatid arms

Cytokinesis in the actin myosin ring

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13
Q

What is aurora a for

A

Spindle integrity

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14
Q

What is aurora b part of

A

Cpc chromosome passenger complex

With incenp, survivin, borealin

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15
Q

Where is aurora b and why

A

Chr arms early eg in mitosis

Moves to centromeres in prometaphase this is so it can aid correct attachment of kinetochores with mt

Via phos of kmn proteins

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16
Q

What spindle attachment is when 1 attaches to each sister

A

Amphitelic

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17
Q

Does amphitelic produce a sac and why

A

No sac is inactive because equal tension

18
Q

What is monotelic

A

When only 1 sister is attached

Produces active sac bc no tension so aurora b present

19
Q

What is syntelic

A

When both mt attach to one sister

Also produces active sac as no tension

20
Q

What is merotelic and why doesn’t this have active sac

A

Both arms attached but 1 has more mt attached

Tension but unequal

21
Q

Which enzyme opposes aurora B action via dephosphorylation

A

Pp1

22
Q

When does pp1 get replaced by aurora b

A

Prophase when aurora b on chr arms

23
Q

What inhibits pp1

A

i2 inhibitor

24
Q

What happens when aurora b moves from arms to centromeres in prometaphase

A

Part of sac

It checks tension. If not there aurora b will cause kinetochore assembly and phos kmn proteins causing proper attachment of k with mt

When this happens anaphase can occur

Aurora b stays in middle of cell and far from kinetochore, allowing kinetochore dissassembly and pp1 increase via i2 degradation from anaphase

25
Q

What is the strong interaction with merotelic and aurora b

A

Because stay in middle, aurora b can phos of kinetochore subunits and allow proper attachment

26
Q

What does sac block which blocks progression to anaphase

A

Apc/cdc20

27
Q

What does securin ub do and how does it allow anaphase

A

Securin degradation activates separase which cleaves cohesin rings around the centromeres = separation

28
Q

Cyclin b causes cdk inactivation and therefore dephos of its substrates , how does this allow anaphase

A

Spindle elongation and allows chr separation to poles

29
Q

How is cdk 1 inactivation good for telophase and mitotic exit

A

Nuclear formation and spindle dissassembly

30
Q

What part of sac blocks apc cdc20

A

Mitotic checkpoint complex mcc

31
Q

What are the key components of mcc

A

Mad 2 closed, bubr1, bub3

32
Q

What does mad2 closed binding to cdc20 do

A

Blocks it’s ability to recognise and degrade cyclin b and securin

33
Q

How are cyclins usually recognised by cdc20

A

N terminal destruction d box

Arg and leucine residues

34
Q

What part of apc also recognises substrates

A

Apc10

35
Q

What occurs for mcc activation

A

Mps1 phosphorylates KNL1

Allows rzz and other binding like bubr1 and bub3

Rzz recruits mad1 and 2

Mad 2 put into a closed complex which binds cdc20

Attracts others like bubr1 and bub3

36
Q

How does physical separation silence the sac

A

Aurora B once phos kmn will allow proper kinetochore attachment

When tension anaphase occurs

Aurora B moves away from kinetochores and stays in middle, allowing pp1 then to dephos and disassemble kinetochores

This silences the sac

37
Q

How does p31 comet silence sac by disrupting mcc

A

Competes with bubr1 for mad2 binding

38
Q

What phosphorylates cdc20 to cause mcc dissassembly and sac turn off

A

Cdk1

39
Q

What is the cdc20 ub dependant path

A

Cdc20 can be degraded via p31 comet ub

Allows mcc fall off and new cdc20 production without silencing

40
Q

What can dephos knl1 platform protein which blocks mcc assembly

A

Pp2a phosphatase

41
Q

How is cyclin a degraded even though sac is turned on in prometaphase nuclear degradation

A

Apc cdc20 can override the sac at this point via long D boxes of cyclin a being recognised

42
Q

What is degraded by cdh1 apc (end of mitosis)

A

Cdc20 , plk, aurora a and b

Cell Bio And Disease (18 decks)

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