Studies on a relationship of uracil and cytosine nucleosides to biosynthesis of deoxyribonucleic acid thymine.

Formate (l), serine (2)) formaldehyde (3), and methionine (4) each can serve as the donor of the carbon atom for the biosynthesis of the methyl group of DNA’-thymine. The utilization of formate for the biosynthesis of DNA in vitro has been reported previously (5-g), and in most instances the uptake of formate carbon under these conditions has been primarily into the methyl group of thymine (5). An investigation has now been made of some of the factors which affect the utilization of formate-Cl4 for the biosynthesis of the methyl group of DNA-thymine in vitro.