[Constraints on base sequences in a polynucleotide: I. Significance of the degeneration of the code].

The statistical study of polynucleotide sequences constituting the genes of E. coli, bacteriophages lambda and T7 reveals that constraints act upon nucleic acids (DNA or RNA) and contribute to determine the choice between the synonymous codons. The existence of synonymous codons seems to be the way of satisfying these constraints, keeping the possibility of specifying a large variety of polypeptides. At least in the case of amino acids with a small number of codons, these constraints are strong enough to influence the primary structure of proteins.