DNA Damage And Repair

Question 1

Cause of DNA damage

Answer 1

ROS, UV light, mutagens, etc

UV light causes formation of pyrimidine dimers

Question 2

Forms of repair

Answer 2

Photo reactivation
Nucleotide Excision repair
Base excision repair
Mismatch repair

Question 3

Nucleotide Excision Repair

Answer 3

Nucleotide excision repair
Distortion of helix recognised by UvrA-UvrB dimer
UvrB unwinds DNA, UvrA released and UvrC is recruited
UvrC excises damaged DNA, Pol I DNA ligase repairs nick

Question 4

Photoreactivation

Answer 4

Photolyase destroys cross link between T-T dimers; FADH- absorbs photon to generate radical that initiates repair

Question 5

Base Excision Repair

Answer 5

Glycosylase detects C to U mutation

Uracil base is excised, DNA pol replaces, sealed by DNA ligase

Question 6

Mismatch Repair

Answer 6

mutS and mutL detect mismatched base

Parental strand recognised by mutH as methylated strand
Faulty base on copied strand recognised and corrected by DNA Pol, sealed by DNA ligase