Nucleic acid changes during the development of the chick embryo.

The chemical changes occurring during embryonic development have been studied by several workers (l-3). In the hen’s egg there is very little nucleic acid present, whereas a considerable synthesis of both desoxypentose nucleic acid (DNA) and ribose nucleic acid (RNA) occurs in the embryo (4-6). Recently, methods for the determination of purines and pyrimidines in small amounts of tissue have become available (7). It occurred to us that a study of the individual purines and pyrimidines in the developing chick embryo might yield important information regarding the composition of the nucleic acids. The present communication gives the results of such a study.