DNA damage/repair

Question 1

Damage to DNA can occur chemically:

Answer 1

deamination of adenine to form hypoxanthine.

Question 2

Damage can occur by oxidation:

Answer 2

creation of 8-oxo-guanine by reactive oxygen species reaction

Question 3

Damage can occur by reaction with an aflatoxin metabolite by:

Answer 3

reaction with a crosslinking reagent such as psorlaen

Question 4

Damage can occur by dimerization:

Answer 4

dimerization of adjacent thymines stimulated by UV light.

Question 5

Damage requires repair system. but another system requiring repair is DNA sliding which:
Lack of repairing this problem leads to what?

Answer 5

occurs amid repeating sequences. Lack of a repair system for these leads to Huntington’s disease

Question 6

DNA repair systems include: (4 things)

Answer 6

1. proofreading
2. mismatch repair
3. nucleotide excision repair
4. base excision repair

Question 7

Proofreading:

Answer 7

It involves 3’-5’ exonucleolytic activity of a DNA polymerase and it ccurs as DNA is being replicated.

Question 8

mismatch repair

Answer 8

fixing of mismatches that occur, largely as a result of errors in replication.

Question 9

Nucleotide Excision Repair

example?

Answer 9

Excision of a group of nucleotides followed by replacement with correct ones by DNA polymerase. ex: Removal of thymine dimers.

Question 10

Base excision repair:

example?

Answer 10

Excision of a damaged base - for example uracil glycosylase removal of U from DNA

Question 11

In E. coli, mismatch repair occurs as a result of action of what three proteins?

Answer 11

• MutS
• MutL
• Mut H

Question 12

What does MutS do?

Answer 12

recognizes mismatch

Question 13

MutL?

Answer 13

recruits MutH

Question 14

MutH?

Answer 14

nicks newly synthesized strand of DNA to allow exonucleolytic removal of nucleotides around the mismatch

Question 15

Nucleotide excision repair can be used to repair ___ ___. Here, a segment of DNA containing the damage is removed by a ___. The gap is then filled in using ___ ____ and ___ ____.

Answer 15

• thymine dimers
• nuclease
• DNA polymerase
• DNA ligase

Question 16

Base excision repair (uracil repair) involves removal of ___ from DNA followed by nicking by an ___, followed by repair by ___ ____ and ___ ____.

Answer 16

• uracil
• endonuclease
• DNA polymerase
• DNA ligase

Question 17

A critical protein for monitoring DNA for damage prior to division is ___. It can ___ the cell cycle if it senses ___ and initiate ____.

Answer 17

• p53
• stop
• damage
• repair

Question 18

If repair by p53 is unable to be performed, it can induce ___ ___/____.

Answer 18

-cellular suicide/apoptosis