Presence of rRNA in the heavy bodies of sea urchin eggs. An in situ hybridization study with the electron microscope.

Experimental conditions have been found, in which the presence of rRNA can be demonstrated by in situ hybridization at the electron microscope level in the heavy bodies of sea urchin eggs. The specificity of hybridization has been controlled by ribonuclease digestion and by competition experiments with unlabelled rRNA.