Carcinogenesis

Question 1

Base Excision Repair

Answer 1

predominant mechanism for spontaneous DNA damage caused by free radicals and other reactive species

damage by alkylation
removes entire base from the DNA strand
uses complementary strand to fill in gap

Question 2

Nucleotide excision repair

Answer 2

e.g. UV light -> thymidine dimer

covalently bound dimers and large adducts: distort DNA structure, impending transcription and replication

segment of strand removed (30-40 nucleotides) -> complementary strand read to fill gap

Question 3

Double stranded breaks

Answer 3

caused by chemicals and ionizing radiation

neither strand can be used as template
can be repaired (DNA ligase IV) but often results in genome rearrangements or cell death

Question 4

Single strand breaks

Answer 4

caused by chemicals and ionizing radiation

undamaged strand used as template (BER or NER)

Question 5

Most reactive sites in DNA

Answer 5

N7 position of guanine and N3 of adenine