PATTERNS OF SYNTHESIS OF DNA-LIKE RNA IN PARTS OF DEVELOPING FROG EMBRYOS

Abstract

Annealing experiments revealed that qualitatively different messenger RNA molecules are synthesized by the animal and vegetal halves of frog blastulae isolated during the period of gastrulation and by the dorsal axial and belly regions of tail-bud embryos cultured for a 24-hour period. Data suggest that differential transcription, rather than translational mechanisms alone, may be a primary control for the selective synthesis of proteins in differentiating embryonic cells. It also appears that the earlier differentiating ectoderm and mesoderm cells of gastrulae produce a greater variety of messenger RNA molecules than do the endoderm cells which differentiate slowly. At the tail-bud stage, however, the cells of the belly region are transcribing more of the DNA sequences than do the cells of the dorsal axial region.