Figure 1. Labeling DNA synthesis and cell division via the de novo nucleotide synthesis pathway.

(a) Schematic of contrasting DNA labeling strategies. The most common approach to tracking DNA synthesis is by accessing the nucleotide salvage pathway with labeled thymidine (e.g. ¹⁵N-thymidine, ³H-thymidine) or halogenated nucleotide analogues (e.g. bromodeoxyuridine-BrdU). In contrast, D-water is incorporated by de novo nucleotide synthesis. (b) During cell division, rapid DNA synthesis coincides with complete replication of the genome, which should lead to rapid D incorporation, exceeding incorporation by maintenance biosynthetic pathways (e.g. protein turnover). During chase, D contained in protein will be diluted by ongoing turnover, whereas signal contained in genomic DNA remains relatively stable until the next cell division.