lec 1. cell cycle

Question 1

mitogens

Answer 1

signals that induce cell to begin cell division

Question 2

growth factors

Answer 2

extracellular signals that control D-type cyclins and drive the G1 phase

Question 3

G0

Answer 3

quiescent state where cell does not proliferate

Question 4

G1 Phase

Answer 4

cell grows in size

cyclin D + Cdk4/6 (G1-Cdk)

Question 5

Restriction Point Cdk complex

Answer 5

cyclin E + Cdk 2 (G1/S-Cdk)

Question 6

S Phase

Answer 6

replicate DNA

cyclin A + Cdk2
cyclin A + Cdk1/Cdc2 (S-Cdk)

Question 7

G2 Phase

Answer 7

grow, prepare to divide

cyclin A + Cdk1/Cdc2 (S-Cdk)

Question 8

M phase

Answer 8

mitosis

cyclin B + Cdk1/Cdc2 (M-Cdk)

Question 9

how the cell cycle is controlled

Answer 9

through levels of cyclins/Cdks and checkpoints

Question 10

Cyclin control of cell cycle

Answer 10

cyclins are controlled by intracellular signals except for D-types which are controlled by extracellular and tell cell whether it should cross restriction point and start proliferating

complexes are also regulated by CKIs which allow cell cycle to move in one direction

Question 11

CDK inhibitors (CKIs)

Answer 11

regulate cyclin/Cdk complexes
- activate complex in next phase, inhibit complex in previous phase

INK family acts on D-type
p57, p27, p21 act on cyclins E, A, B

Question 12

3 checkpoints in cell cycle

Answer 12

1) G1/S restriction point
2) G2/M checkpoint
3) metaphase/anaphase checkpoint

Question 13

restriction point

Answer 13

At G1/S:

D + Cdk 4 hypophosphorylate E2F. E cyclin dissociates E2F which then transcribes gene to send cell into S-phase

Question 14

3 places where DNA damage is spotted

Answer 14

1) G1
2) entry into S
3) entry into mitosis

Question 15

chromosome non-disjunction

Answer 15

failure of homologous or sister chromatids to separate correctly

Question 16

how radiation causes DNA damage

Answer 16

it breaks DNA which activates ATM/ATR, and Chk1/Chk2 kinases which activate p53 and then turn on p21 which inactivates G1/S-Cdk and S-Cdk

Question 17

2 problems with DNA replication

Answer 17

1) DNA has to be replicated accurately

2) DNA must only be copied once

Question 18

licensing

Answer 18

inactive helicases are put onto replication origins to form a PreRC in G1, and then are activated by S-Cdk -> this ensures DNA is replicated once

Question 19

differences in cell cycle during development

Answer 19

cyclins E and A maintain high levels in the wrong place. As a result, Rb is hyperphosphorylated which drives a short G1, and CKIs are expressed at low levels.

Question 20

DNA repair in G1 and G2

Answer 20

G1: non-homologous end joinging
G2: homologous recombination