Synthesis of RNA by male pronuclei of fertilized sea urchin eggs.

Experiments have been conducted in an effort to determine when the paternally derived genome of sea urchin embryos becomes active in RNA synthesis. Participation of the paternal genome in RNA transcription as early as fertilization has been indicated by the following: (1) polyspermic zygotes consistently demonstrate greater levels of incorporation of labelled precursor (3H-uridine) into RNA when compared to monospermic eggs. (2) Monospermic and polyspermic eggs treated with actinomycin D show the same levels of incorporation of label into RNA. (3) Analysis of autoradiographs demonstrates the incorporation of 3H-uridine into male and female pronuclei.