11 - Cell Cycle Checkpoints

Question 1

If you were a normal cell dividing, what do you want to check?

Answer 1

DNA at G2 (after S-phase) = to see if DNA pol made a mistake = mismatches &raquo_space;> need repairs

Question 2

What is one reason explaining why one mutation is never enough to cause a cell to transform into a cancer cell?

Answer 2

cell has a lot of tumor-suppressors

Question 3

What does Wee1 kinase do?

Answer 3

pauses cell cycle by phosphorylating CDK = changes shape so it doesn’t work

Question 4

What does Cd25 phosphatase do?

Answer 4

resumes cell cycle by dephosphorylating CDK = change shape = works again

Question 5

What will happen to a cell due to a Wee1 mutation?

Answer 5

cells will be smaller but more of them | because they did not have enough time to check and grow to right size

Question 6

What will happen to a cell due to a Cd25 mutation?

Answer 6

cannot reactivate CDK = cells are larger and does not divide | larger = bc had so much time to grow

Question 7

What are CKIs? What is an example of one?

Answer 7

CDK complex inhibitor | ex: p27 | inactivates CDK-cyclin complex by latching onto it = renders it inactive

Question 8

What is the status of CDK in non-proliferating cells?

Answer 8

held inactive by CKI &raquo_space;> Rb = active = no free E2F = no cyclins made

Question 9

What is the status of CDK in proliferating cells?

Answer 9

CKI = inactive &raquo_space;> CDK = active; Rb = active = release E2F = cyclins made &raquo_space;> expression of S-phase genes activated

Question 10

What is non-disjunction?

Answer 10

chromatids don’t separate because spindles are not working = aneuploidy

Question 11

What is APC?

Answer 11

protein that tags ubiquitins on securin to activate separase

Question 12

What is separase?

Answer 12

cleaves the cohesins that hold the chromatids together

Question 13

What is securin?

Answer 13

sequesters and inactivates separase

Question 14

What would happen if we went into G1 and all of our M-cyclins are still there?

Answer 14

cell will skip S-phase and divide again

Question 15

Which cells do not make M-cyclins and why?

Answer 15

germ cells = they don’t undergo S-phase (only meiosis)

Question 16

What is the most common type of DNA damage?

Answer 16

double-stranded breaks

Question 17

What are ATM and ATR?

Answer 17

detectors for detecting DNA damages and

Question 18

What are 2 damages that ATR detects and what does it do?

Answer 18

TT dimers and stalled replication forks | brings in NER to fix TT dimer

Question 19

What damage can ATM detect? What will it do?

Answer 19

double strand breaks | will initiate NHEK+J and HR pathways

Question 20

What is the BRCA1 protein?

Answer 20

scaffolding protein that helps a network

Question 21

What are Chk1 and Chk2 proteins?

Answer 21

intermediary proteins involved in the ATM/ATR detection process

Question 22

What effect can ATM have on MDM2?

Answer 22

can induce phosphorylation of MDM2