Evidence for the appearance of novel gene products during amphibian blastulation

Genetic information begins to be transcribed during early cleavage in amphibian embryos,(1,2) and the tempo of informational RNA synthesis increases gradually through cleavage and into the early blastula stage. Previous studies from this laboratory (3,4) have shown that at this point a remarkable, near embryo-wide acceleration of informational RNA synthesis occurs, resulting during the mid-tolate blastular period in at least a 20-fold increase in the rate of synthesis of heterogeneously sedimenting, DNA-like RNA.