Abstract
Summary “Nearest neighbor” base pairs (“doublets”) in the protein-coding regions of MS2 RNA have been tabulated with respect to their positions in the first two bases of amino acid codons, in the second two bases, or paired by contact between adjoining codons. Considerable variation is evident between numbers of doublets in each of these three possible positions, but the totals of each of the 16 doublets in the coding regions of the MS2 RNA molecule show much less varation. Compilations of doublets in nucleic acid strands have no predictive value for the amino acid composition of proteins coded by such strands.