Biosynthesis of J occurs in two steps: in the first step, a specific thymidine in DNA is converted into hydroxymethyldeoxyuridine; in the second, HOMedU is glycosylated to form J. Proteins that bind specifically to this base have been identified.
Biosyntese af J sker i to trin: i det første trin konverteres en specifik thymidin i DNA til hydroxymethyldeoxyuridin; i det andet glykosyleres HOMedU til at danne form J. Der er blevet fundet proteiner, der binder specifikt til denne base.