A 10 year old child experiences recurrent skin lesions on her face and upper extremities that rapidly progress to cancer. Xeroderma pigmentosa is considered a possible differential. Which of the following is defective in that case
UV rays damage DNA by forming thymidine dimers. This is repaired by the body by nucleotide excision repair. Main enzyme of this mechanism is UV-specific endonuclease.
Topoisomerase
3' → 5' Exonuclease
Endonuclease
Helicase