Gene expression in chick morula.

The polypeptides synthesized during the morula stage in the chick embryo are insensitive to transcriptional inhibition by α-amanitin. Protein synthesis seems to depend predominantely, if not exclusively, on the recruitment of maternal mRNA, rather than on embryonic gene expression in chick morula. The morula embryo expresses the heatshock polypeptides when stressed at 43°C. The heat-induced polypeptides are isoforms of polypeptides that are synthesized normally. These polypeptides are α-amanitin sensitive and appear to mark the first major expression of the embryonic genome in the chick embryo.