100 methyltransferase reactionsThe common feature of all megaloblastic anemias is a defect in DNA synthesis that affects rapidly dividing cells in the bone marrowAll conditions that give rise to megaloblastic changes have in common a disparity in the rate of synthesis or availability of the four immediate precursors of DNAIn deficiencies of either folate or cobalamin. there is failure to convert deoxyuridine monophosphate (dUMP) to deoxythymidine monophosphate (dTMP), the precursor of dTTPThis is the ease because folate is needed as the coenzyme 5,10-methylene-THE polyglutamate for conversion of dUMP to dTMP: the availability of 5,10-methylene-THF is reduced in either cobalamin or folate deficiency.">