This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Metabolism of nucleic acids, Subject name: Biochemistry
[{'content': 'Effect of ultraviolet radiation on DNA is formation of \nSelect and explain. \nA. Purine dimers, B. Pyrimidine dimers, C. DNA-DNA cros linking, D. All of the above', 'role': 'user'}, {'content': 'Answer: B \nExplanation: UV light causes the formation of thymine dimers, where covalent bonds are formed between adjacent thymine residuesSince repair mechanism is not operating these mutations are accumulated, leading to cancerRef: DM Vasudevan, 7th edition, page no: 584', 'role': 'assistant'}]