This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Proteins and Amino Acids, Subject name: Biochemistry
DNA repair defect is seen in: 
Select and explain. 
A. Xeroderma pigmentosum, B. Li-fraumani syndrome, C. Retinoblastoma, D. None
A: Xeroderma pigmentosum
Answer: A: Xeroderma pigmentosum 
Explanation: Ans. (a) Xeroderma pigmentosumRef: Harper's Biochemistry, 30th ed. pg. 389-90, 28th ed.pg. 330-32* Xeroderma pigmentosum is an autosomal recessive genetic disease which arises due to defect in DNA repair particularly of thymidine dimers.Examples of Conditions Arising due to DNA Repair Defects:* Xeroderma pigmentosa* Ataxia telangiectasia* Fanconi's syndrome* Bloom syndrome* HNPCC