Week 4

Question 1

Anaphase promoting complex increases ubiquitin activity
how does this affect cohesin?

Answer 1

leads to cleavage of cohesin
–beginning of sister chromatid separation

Question 2

role of cdc25 in M-CDK activity
- hint: triggers early mitosis

• role of CAK on M-CDK

Answer 2

cdc25 is phosphatase that removes inhibitory WEE1 phosphorylation
— CAK activates M-CDK via phosphorylation

Question 3

role of cohesin in prepping chromosome for mitosis
- i.e. at S phase

Answer 3

formation of cohesin complex in S phase leads to bi-orientation of sister chromatids

Question 4

SCC1 cohesin component connects SMC3,1 ATPase domains

result of SCC1 mutations?

Answer 4

– precocious sister-chromatid separation

Question 5

effect of following on mt stability
Mt associated proteins MAPS
- catastrophe factors K8,K13

Answer 5

• MAPs– promote mt elongation/growth at plus end

K8/13– depolymerization

Question 6

describe the state of kinetochore mts at

metaphase

anaphase

Answer 6

• metaphase– mts remain stable, constant length— steady flux

anaphase– rapid mt shortening via depolym. at both ends

Question 7

role of following motor proteins

K5,K14

K4,K10

Dynein

Answer 7

• K5,K14– bridge interpolar mts and facilitate sliding– regulate spindle length

K4,K10– chromokinesins push chromosome arms towards metaphase plate

Dynein– minus end directed, pulls centrosome towards cell cortex– spindle separation

Question 8

role of Mitotic checkpoint complex in the event of unattached kinetochore
i.e how does it PREVENT anaphase

Answer 8

inhibits the activation of APC/C—>separase remains inactive—> cohesin SCC1 is not cleaved

Question 9

what provides kinetochore protection at meiosis 1 so that sister chromatids are not separated until meiosis 2?

Answer 9

Shugoshin-PP2
- formation of chiasmata between homologous regions of sister-chromatids— contributes to homologous recombination

Question 10

what are centromeres and what makes them special?

Answer 10

chromosome regions assisting in kinetochore assembly
– contain a H3 histone variant CENP-A
- give it specific function

Question 11

what are two triggers of cytokinesis and subsequent cleavage furrow via actin-myosin contractile ring

Answer 11

• loss of M-CDK
• loss of central spindle

Question 12

what is the role of centralspindlin, Ect2 in promoting actin-myosin contractile ring

Answer 12

– promotes RhoA small GTPase—> activates pathways for actin polymerization, myosin activity