Methylation of nucleolar RNA during development of the amphibian oöcyte

Transmethylation is known to occur from methionine to ribonucleic acid (RNA) derivatives (Fleissner & Borek, 1962). Most of these methylated derivatives are typical of transfer RNA (Dunn, 1959). In dipteran salivary cells it was possible to distinguish with autoradiography between the transmethylation to RNA and the incorporation of methionine into protein (Sirlin, Jacob & Tandler, 1963). The same approach was used in the present experiments to trace the formation of transfer RNA in amphibian oöcytes.