DNA repair

Question 1

Nucleotide excision repair

Answer 1

Endonuclease removes area around pyrimidine dimer
DNAP
DNALigase

Occurs in G1

Dimers from UV light (process impaired in Xeroderma Pigmentosum)

Question 2

Base excision repair

Answer 2

Base specific glycosylase removes base leading to AP site
AP-endonuclease removes sugar string at 5’
Lyase removes sugar string at 3’
DNAP-beta fills gap
DNA Ligase seals

Occurs throughout cell cycle

Repairs spontaneous/toxic deamination (wrong base occurs where a good one was)

GEL PLease

Question 3

ssMMR

Answer 3

G2
Recognize new strand and MM nucleotides removed
filled and resealed

Lynch syndrome

Question 4

dsDNA break repair

Answer 4

binds loose ends, no requirement for homology, lose some material

Defective in ataxia telangectasia
BRCA1
Fanconi anemia