Mitosis Phase

Question 1

What is stopped from getting degraded in the spindle assembly checkpoint

Answer 1

Cyclin b and securin (allowing anaphase)

Question 2

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

Answer 2

Nuclear is a

Cytoplasmic is b

Question 3

When does cyclin a get degraded

Answer 3

Before prometaphase

Question 4

When does cyclin b increase / peak and then lower

Answer 4

Peak is at prometaphase

Low is met- anaphase

Question 5

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

Answer 5

Cdc25b

Question 6

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

Answer 6

Polo like kinase

Question 7

What does plk do in respect to cdk 1 activation

Answer 7

Phos of wee and myt inhibiting them

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

Question 8

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

Answer 8

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

Plk then causes a loop via phos of cdc25c

Question 9

How many centrioles are from centrosomes

Answer 9

2

Question 10

Explain centrosome cycle which duplicates for mitosis

Answer 10

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

Question 11

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

Answer 11

Centrosome maturation via plk4

Question 12

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

Answer 12

Prophase pathway of cohesin ring removal on sister chromatid arms

Cytokinesis in the actin myosin ring

Question 13

What is aurora a for

Answer 13

Spindle integrity

Question 14

What is aurora b part of

Answer 14

Cpc chromosome passenger complex

With incenp, survivin, borealin

Question 15

Where is aurora b and why

Answer 15

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

Question 16

What spindle attachment is when 1 attaches to each sister

Answer 16

Amphitelic

Question 17

Does amphitelic produce a sac and why

Answer 17

No sac is inactive because equal tension

Question 18

What is monotelic

Answer 18

When only 1 sister is attached

Produces active sac bc no tension so aurora b present

Question 19

What is syntelic

Answer 19

When both mt attach to one sister

Also produces active sac as no tension

Question 20

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

Answer 20

Both arms attached but 1 has more mt attached

Tension but unequal

Question 21

Which enzyme opposes aurora B action via dephosphorylation

Answer 21

Pp1

Question 22

When does pp1 get replaced by aurora b

Answer 22

Prophase when aurora b on chr arms

Question 23

What inhibits pp1

Answer 23

i2 inhibitor

Question 24

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

Answer 24

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

Question 25

What is the strong interaction with merotelic and aurora b

Answer 25

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

Question 26

What does sac block which blocks progression to anaphase

Answer 26

Apc/cdc20

Question 27

What does securin ub do and how does it allow anaphase

Answer 27

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

Question 28

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

Answer 28

Spindle elongation and allows chr separation to poles

Question 29

How is cdk 1 inactivation good for telophase and mitotic exit

Answer 29

Nuclear formation and spindle dissassembly

Question 30

What part of sac blocks apc cdc20

Answer 30

Mitotic checkpoint complex mcc

Question 31

What are the key components of mcc

Answer 31

Mad 2 closed, bubr1, bub3

Question 32

What does mad2 closed binding to cdc20 do

Answer 32

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

Question 33

How are cyclins usually recognised by cdc20

Answer 33

N terminal destruction d box Arg and leucine residues

Question 34

What part of apc also recognises substrates

Answer 34

Apc10

Question 35

What occurs for mcc activation

Answer 35

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

Question 36

How does physical separation silence the sac

Answer 36

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

Question 37

How does p31 comet silence sac by disrupting mcc

Answer 37

Competes with bubr1 for mad2 binding

Question 38

What phosphorylates cdc20 to cause mcc dissassembly and sac turn off

Answer 38

Cdk1

Question 39

What is the cdc20 ub dependant path

Answer 39

Cdc20 can be degraded via p31 comet ub Allows mcc fall off and new cdc20 production without silencing

Question 40

What can dephos knl1 platform protein which blocks mcc assembly

Answer 40

Pp2a phosphatase

Question 41

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

Answer 41

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

Question 42

What is degraded by cdh1 apc (end of mitosis)

Answer 42

Cdc20 , plk, aurora a and b