Uridineinbau in die Nucleinsäuren von Furchungsstadien der Eier des Seeigels Paracentrotus Lividus

Abstract

1. Uridine taken up during the 16^th-cell stage of the sea urchin egg is stored in acid soluble form. 2. During the interphase of this stage uridine is used for an RNA-synthesis in the micromeres, the smallest blastomeres of the egg, which have a prolonged interphase. There seems to occur no RNA-synthesis in the other blastomeres of this stage or the synthesis in these cells is considerably smaller. The RNA of the micromeres has a high turnover, it is neither tRNA nor rRNA but probably mRNA. 3. 2½ hours after the 16^th-cell stage — this is in the young blastula stage — about 5½ hours after fertilization, at least half of the micromere-RNA is already decomposed, the fission products of which having been used together with the stored uridine to synthesize rRNA and (after methylation of the uridine) DNA.