Which vitamin is essential for DNA synthesis and is often supplied as folic acid?

Which vitamin is essential for DNA synthesis and is often supplied as folic acid?

• A. Vitamin B6
• B. Vitamin B5
• C. Vitamin B9
• D. Vitamin B12

Answer: (C)

DNA synthesis relies on folate because its active forms donate one-carbon units essential for making the building blocks of DNA, specifically thymidylate (dTMP) and purines. The reaction that converts dUMP to dTMP uses 5,10-methylene-THF, a process central to DNA replication, especially in rapidly dividing cells. Because of this, adequate levels of folate are crucial, and deficiency leads to impaired DNA synthesis and megaloblastic anemia. Folate is often supplied as folic acid in supplements and fortified foods; after absorption, it’s converted into THF forms that participate in one-carbon metabolism. Other B vitamins have different primary roles—B6 in amino acid metabolism and neurotransmitter synthesis, B5 in formation of coenzyme A, and B12 in methylation and odd-chain fatty acid metabolism—so none are as directly tied to DNA building blocks as vitamin B9. It’s also worth noting that B12 helps regenerate THF from a form that temporarily traps folate, linking the two vitamins in maintaining DNA synthesis capacity.

DNA synthesis relies on folate because its active forms donate one-carbon units essential for making the building blocks of DNA, specifically thymidylate (dTMP) and purines. The reaction that converts dUMP to dTMP uses 5,10-methylene-THF, a process central to DNA replication, especially in rapidly dividing cells. Because of this, adequate levels of folate are crucial, and deficiency leads to impaired DNA synthesis and megaloblastic anemia. Folate is often supplied as folic acid in supplements and fortified foods; after absorption, it’s converted into THF forms that participate in one-carbon metabolism. Other B vitamins have different primary roles—B6 in amino acid metabolism and neurotransmitter synthesis, B5 in formation of coenzyme A, and B12 in methylation and odd-chain fatty acid metabolism—so none are as directly tied to DNA building blocks as vitamin B9. It’s also worth noting that B12 helps regenerate THF from a form that temporarily traps folate, linking the two vitamins in maintaining DNA synthesis capacity.