30_DNA Damage & Cell Cycle Checkpoints

Question 1

What are the cell’s three reactions to DNA damage?

Answer 1

1) repair
2) activate checkpoint, arrest cell cycle
3) apoptosis

Question 2

The cell cycle halts if two critical events are incomplete; what are they?

Answer 2

DNA replication in S phase

Chromosome alignment during M phase

Question 3

What is the inheritance pattern of ataxia-telangiectasia?

Answer 3

recessive

Question 4

What type of radiation are patients with AT sensitive to?

Answer 4

ionizing radiation (causing dsDNA breaks)

Question 5

Which gene is mutated in AT patients?

Answer 5

ATM

Question 6

What are ATM and ATR activated by?

Answer 6

ATM: dsDNA breaks
ATR: ssDNA breaks

Question 7

What type of DNA damage does UV radiation induce?

Answer 7

ss-DNA breaks

Question 8

Which type of radiation induces double-stranded DNA breaks?

Answer 8

ionizing radiation

Question 9

Which checkpoint kinases do ATM and ATR activate?

Answer 9

ATM: Chk2
ATR: Chk1

Question 10

Which protein is dubbed the “guardian of the genome”? At which stage does it arrest the cell cycle?

Answer 10

p53

G1 => S

Question 11

Cdc25 is a (kinase/phosphatase).

Answer 11

phosphatase

Question 12

What effect does phosphorylation have on cdc25?

Answer 12

results in its shuttling to the cytoplasm. CDK complex remains inactive, and cell cycle is arrested at G2-M.

Question 13

Is p53 stable in its phosphorylated or dephosphorylated form?

Answer 13

phosphorylated

Question 14

As a result of phosphorylation of p53, what genes are transcribed more?

Answer 14

p21 - CDI & Bax

Question 15

What does p21 CDI inhibit?

Answer 15

G1 and S CDKs

Question 16

What is the consequence of Bax upregulation?

Answer 16

apoptosis

Question 17

Which effector is involved in arresting the cell cycle at the G2-M checkpoint?

Answer 17

cdc25