Synthesis of nucleic acid purines in the sea urchin embryo

Embryos of the sea urchin, Arbacia punctulata, were shown to utilize carboxyl labeled acetate and glycine for the synthesis of nucleic acids and protein.The hypothesis that DNA must arise exclusively from the pre-formed RNA of the virgin egg is unlikely since the specific activities of DNA and its isolated purines from the blastula were at least 10 times greater than the corresponding values for RNA.The specific activities of adenine and guanine of RNA formed from glycine-1-C¹⁴ were identical, whereas in DNA the specific activity of adenine was less than half that of guanine.Comparison of the specific activities of the DNA purines with the glycine in the medium indicated that a large part of the newly formed DNA arose from unlabeled endogenous precursor.