This proposal aims to study the effects of estradiol on protein synthesis in the developing cockerel liver. In young animals the liver contains a proportionally large excess of monosomes which do not participate in protein synthesis. Injection of hormone causes a rapid transfer of monosomes to polysomes and a large increase in protein synthesis. This is accompanied by the induction of a new gene product, vitellogenin, the precursor of egg yolk protein. Induction can take place only in cockerels older than two weeks and weighing at least 100g. The induction is linked to development. The rate of synthesis of vitellogenin at the peak of induction is 60% of all liver secreted proteins. This amount is brought about by additional synthetic activity over and above that of uninduced liver. This feature potentially allows for the isolation of the molecular elements involved in the activation of protein synthesis and in specific protein synthesis, including specific polysomes and mRNA. It allows the analysis of potentially regulated steps in the transcription and translation of specific mRNA as affected by developmental and hormonal variables.