cell cycle

Question 1

in which stage is the commitment point?

Answer 1

G1

Question 2

what are cyclins?

Answer 2

proteins that are synthesized and degraded in a cell cycle dependent manner, control the activity of cyclin dependent kinases (activate and direct to substrate)

Question 3

which cyclin is directly responsive to growth factors?

Answer 3

cyclin D

Question 4

which cyclin-CDKs are in G1?

Answer 4

cyclin D-CDK4
cyclinD-CDK6
(restriction point)
cyclin E-CDK2

Question 5

which cyclin-CDKs are in S?

Answer 5

Cyclin A- CDK2

Question 6

which cyclin-CDKs are in G2?

Answer 6

Cyclin A-CDK1

Cyclin B-CDK1

Question 7

how do cyclins activate CDKs?

Answer 7

cyclin binding results in conformational change that allows for APT binding and exposure of a phosphorylation site on the T loop

Question 8

primary role of cyclinD-CDK4/6 complexes

Answer 8

inactivate Rb protein so that E2F is released

Question 9

what is E2F?

Answer 9

replication factor that controls the expression of DNA replication enzymes as well as cyclins D, E and A

Question 10

what defines the “restriction point”?

Answer 10

when a positive feedback loop has been set by cyclin D and growth factors are no longer required for division

Question 11

which cyclin-CDK complex allows for full activation of E2F?

Answer 11

cyclin E-CDK2 that accumulates at the end of G1

Question 12

why are high levels of E2F required for the activation of cyclin A?

Answer 12

cyclin A promoter only weakly binds E2F

Question 13

what is responsible for “licensing” and what occurs?

Answer 13

cyclin E-CDK2 is responsible

assembly of complex including ORC, cdc6, cdt1 and MCM complex forms

Question 14

what triggers replication in S phase?

Answer 14

cyclin A-CDK2 complex

Question 15

what is another “term” for cyclin B-CDK1?

Answer 15

MPF

Question 16

what controls the activity of cyclin B-CDK1?

Answer 16

wee1- kinase

cdc25- phosphatase

Question 17

what is the action of Wee1 kinase?

Answer 17

adds inhibitory phosphate residue to Y15 and will stop cell from dividing if too small

Question 18

what is the action of cdc25 phosphatase?

Answer 18

removes phosphate from Y15 allowing for division to proceed

Question 19

what is the inhibitory site of CDK1? activating site?

Answer 19

inhibitory- Y15

activating- T161

Question 20

what allows for disassembly of the nuclear envelope?

Answer 20

phosphorylation of lamin network

Question 21

what will contribute to chromosome condensation?

Answer 21

condensin phosphorylation

Question 22

what will trigger formation of mitotic spindle?

Answer 22

phosphorylation of microtubule assoc proteins

Question 23

what is APC/C?

Answer 23

anaphase promoting complex cyclosome

Question 24

what are the 2 targets of APC/C?

Answer 24

1- anaphase inhibitor, securin

2-cyclin B

Question 25

what is the action of APC/C on securin?

Answer 25

securin blocks the activity of seprase

APC/C will remove securin from seprase to allow for chromosome separation

Question 26

what is the action of APC/C on cyclin B?

Answer 26

will trigger ubiquitination and degradation (cyclin B must be degraded if cell is going to go on to divide again)

Question 27

what targets APC/C to securin?

Answer 27

cdc20

Question 28

what targets APC/C to cyclin B?

Answer 28

cdh1

Question 29

during what phase of mitosis does APC/C activity begin?

Answer 29

metaphase