Ribosomal RNA Synthesis and the Multiple, Atypical Nucleoli in Cleaving Embryos

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Science  05 Mar 1971:
Vol. 171, Issue 3974, pp. 898-901
DOI: 10.1126/science.171.3974.898


The rate of ribosomal RNA synthesis per nucleus in cleaving sea urchin embryos is similar to the rate at later embryonic stages. The multiple, atypical nucleoli, present in early embryos and usually attributed to decreased ribosomal RNA synthesis, are beginning stages of nucleolar formation. Full nucleolar development requires more time than the brief interphase of the rapidly dividing cells.