Multiple Choice
In DNA repair pathways, DNA repair enzymes most directly use which of the following as their substrate?
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17. Mutation, Repair, and Recombination
DNA Repair
Multiple Choice
In the context of DNA repair, which vitamin is most directly required as a cofactor for thymidylate synthase to support nucleotide synthesis during DNA replication and repair?
A
Folate (vitamin B9)
B
Vitamin A (retinol)
C
Vitamin D (cholecalciferol)
D
Vitamin C (ascorbic acid)
Verified step by step guidance1
Understand the role of thymidylate synthase in DNA synthesis: it catalyzes the conversion of deoxyuridine monophosphate (dUMP) to deoxythymidine monophosphate (dTMP), which is essential for DNA replication and repair.
Recognize that thymidylate synthase requires a methyl group donor to convert dUMP to dTMP, and this methyl group is provided by a cofactor derived from folate metabolism.
Identify folate (vitamin B9) as the vitamin that is converted into tetrahydrofolate (THF), which acts as a carrier of one-carbon units, including the methyl group needed by thymidylate synthase.
Note that other vitamins listed (A, D, C) do not participate directly in the methylation process required for thymidylate synthase activity or nucleotide synthesis.
Conclude that folate (vitamin B9) is the vitamin most directly required as a cofactor for thymidylate synthase to support nucleotide synthesis during DNA replication and repair.
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