Poly (A)-containing RNA Synthesis in Xenopus laevis Embryos

Poly(A)-containing RNA synthesis was studied in isolated cells from Xenopus laevis embryos at various stages of early development. Sedimentation analysis revealed little stage-dependent differences in the distribution; the size was heterogeneous and ranged from >40S to 18S, with an average of 25S (ca. 1.4 × 106 daltons). The total amount of newly synthesized poly(A)-containing RNA increased sharply as development proceeded. On a per-cell basis, however, the synthesis of poly(A)-containing RNA was much more active in blastula cells than in later embryonic cells.