Polypeptide synthesis in sea urchin embryogenesis: an examination with synthetic polyribonucleotides.

After fertilization of the sea urchin egg the rate of protein synthesis by a cell-free ribosomal system increases markedly. This increase can be attributed to newly synthesized messenger RNA, since (i) the rate of polypeptide synthesis elicited by synthetic messenger polyribonucleotides changes only slightly after fertilization, and (ii) the enzymes for the formation of amino acyl transfer RNA's of phenylalanine and leucine and the polymerization of polypeptide are in excess in the unfertilized egg. Polypeptide synthesis has been characterized in development to the gastrula stage.