This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Regulation of Gene Expression , Subject name: Biochemistry
[{'content': 'Xeroderma pigmentation is caused due to a group of closely related abnormalities in - \nSelect and explain. \nA. Mismatch repair, B. Base excision repair, C. Nucleotide excision repair, D. SOS repair', 'role': 'user'}, {'content': "Answer: C \nExplanation: Ans. is 'c' i.e., Nucleotide excision repairo This question is repeat from AIIMS-2005Nucleotide excision repairo UV rays cause DNA damage by forming TT dimmers which prevent replication,o Enzyme UV specific endonclease (UVr ABC excinuclease) cleaves the damaged strand on both sides,o DNA polymerase fills the gap & DNA ligase seals the nick. Example of disease associated with defective nucleotide excision repair is xeroderma pigmentosum. Due to defecdve nucleotide excision repair, there is formation of bulky DNA lesions as a result of formation of thymidine dimers caused by UV rays induced damage.", 'role': 'assistant'}]