PROPERTIES OF NUCLEAR RNA IN SEA URCHIN EMBRYOS*
Abstract
Pulse-labeled RNA in early sea urchin embryos (64 cells to mesenchyme blastulase) is found almost exclusively associated with the nucleus and turns over very rapidly. The rate of labeling of the cytoplasm is much slower and is consistent with the transfer of 6 per cent of the nuclear RNA made every 15-20 minutes. Most of the pulse-labeled nuclear RNA exists in membrane-bound polyribosomes.
