;!"P Distribution in Oligonucleotides of 28 S Ribosomal RNA of the Novikoff Hepatoma and Normal Rat Liver1

35 S, and 28 S RNA of tumors is characterized by a lower adenylic acid content and a higher cytidylic acid content than that of nontumor tissues (3). In addition, it was found that the isotope content of the dinucleotides GC and GU of hepatomas was significantly higher than that of normal liver (18). For determination of whether these differences represented isotope effects or seg mentai differences in these large molecules, studies were made on other dinucleotides, as well as studies of longer segments of these molecules. The isotope content of the dinucleotides AC and AU were not significantly dif ferent in hepatomas and normal liver (18). The present study shows that in the B:) fragment (which is 600 nucleotides long) of the Novikoff hepatoma and in normal liver there are no significant differences in J2P nucleo tide composition or in isotope content of the oligonucleotides. Accordingly, the differences found in nucleolar RNA's of tumors and other tissues represent segmental