Evidence for the Existence of Two Types of Ribonucleic Acid

Abstract

THE predominant internucleotide link in ribonucleic acids is now known to be a phosphodiester link between the 3′ position of one nucleoside residue and the 5′ position of the neighbouring residue, regardless of whether the nucleoside residue contains a purine or a pyrimidine¹. Assuming for the moment that all the nucleic acid chains have equivalent numbers of base and phosphate residues, the chains may be built up in one of two ways. These are represented diagrammatically in formulæ I (a and b) and II, where C₂, C₃ and C₅ represent positions 2′, 3′ and 5′ of the nucleoside residues, (P) a phosphate group; in each case the two terminal and one internal nucleoside residues are depicted.