Topic 2 Molecular Genetics: Repair Mechanisms

Question 1

• DNA polymerase checks base pairs

Answer 1

Proofreading

Question 2

• Enzymes repair the errors DNA polymerase missed — mismatch repair deals with correcting mismatches between normal bases

Answer 2

Mismatch Repair

Question 3

• Enzymes remove nucleotides damaged by mutagens

Answer 3

Excision Repair

Question 4

a. Nucleotide excision repair

b. Base excision repair

Answer 4

Types of Excision Repair

Question 5

• Can be used to repair issues like thymine dimers

Answer 5

a. Nucleotide excision repair

Question 6

• Similar in function to nucleotide excision repair, but uses different enzymes. The main difference is that nucleotide excision repair will chunk out an entire segment around the faulty base by nicking the entire surrounding phosphodiester backbone, not just the faulty base.
• Base excision repair first chunks out just the faulty base, then the phosphodiester backbone around the base is cut out, then polymerase I does some 5’ to 3’ exonuclease cutting and fills in the gaps

Answer 6

b. Base excision repair