DNA Replication

Question 1

Benzo[a]pyrine

Answer 1

Mutagenic agent found in cigarette smoke and grilled meats that causes G to T substitution

Repaired by NER

Question 2

Nucleotide Excision Repair

Answer 2

XPD (ERCC2) is 5’ –> 3’ helicase that forms denaturation bubble around mutations. Endonuclease digestion on either side of lesion followed by exonuclease removal and DNA polymerase to repair DNA.

Question 3

UV Irradiation as carcinogen

Answer 3

Sunlight exposure –> neighboring thymines catalyzed to form dimer –> repaired by NER

Question 4

Mutator hypothesis

Answer 4

Mutation in a gene that is involved in DNA repair increases the likelihood of additional mutations occurring that cannot be repaired.

Question 5

Base excision repair

Answer 5

Deamination of cytosine –> uracil
Deamination of methylated cytosine –> thymine

1) Glycosylase cuts sugar of nucleotide
2) Endonuclease cuts DNA strand
3) Polymerase adds correct nucleotide
4) Exonuclease removes extra fragment
5) Ligase joins strands together