Abstract
The amino acid composition of four phages, five bacteria, one alga, and one protozoon was compared to the frequency of occurrence of the doublet nucleotide sequences in these organisms, and 26 doublet sequences were found to be significantly correlated to one or another amino acid at the 95 per cent or better level of confidence. These data have been used in conjunction with genetic information to formulate codons with nucleo-tides of fixed sequence.