This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Biochemistry
[{'content': 'What is involved in formation of d-TMP from d-UMP? \nSelect and explain. \nA. N5, N10-methylene tetra hydrofolate, B. Form imino folate, C. N5 formyl folate, D. Dihydro folate', 'role': 'user'}, {'content': 'Answer: A \nExplanation: A i.e. N5 - N10 methylene tetrahydrofolated-UMP (deoxy-uridine monophosphate) is conveed to d-TMP (deoxy-thymidine monophosphate) which uses N5, N10 -methylene tetra hydrofolate as a source of methyl group (1 carbon & 2 hydrogen)Q.). This is an unusual reaction in that THF (tetrahydrofolate) contributes not only 1 carbon unit but also 2 hydrogen atoms from pteridine ring , which causes oxidation of THF to DHF. Disorders of folate & vitamin B12 metabolism cause deficiency of TMP.Thymine analog, antitumor drug 5-flurouracil (5Fu) is conveed to 5-F dUMP, which becomes permanently bound to the inactive thymidylate synthaseQ. So 5FU is a suicide inhibitor. Methotrexate (Mtx) and antibacterial trimethoprim inhibits dihydrofolate reductase, an enzyme which reduces DHF to THFQ.', 'role': 'assistant'}]