Folic acid from the diet is reduced to dihydrofolate (DHF) via dihydrofolate synthase, then to tetrahydrofolate (THF) via dihydrofolate reductase (DFHR). Serine hydroxymethyltransferase converts L-serine to glycine and donates the resulting methyl group to THF to create Me-THF, a molecule that serves as a source for a methyl group in several cellular reactions. Me-THF gives up its carbon and is oxidized to DHF via thymidylate synthase (TS) in the process of synthesizing dTMP from dUMP. DHF is reduced back to THF via DHFR, resetting the cycle to continue facilitation of methyl donations for dTMP, and ultimately DNA synthesis.