Figure 3. Phylogenetic analysis of codon identity functions in tRNA.

A. Degenerate genetic code table painted with colors describing the ancestry (S) of their codon identity function, in which two (A) or one (B) position in the codon is degenerate and harbors any one of the four bases (N). Ancestries were derived by constraining sets of tRNA molecules into monophyletic groups. S values are provided in the right hand corner for every codon, and corrected S values that exclude type I molecules from the constraints are given in the left hand corner for codons related to Leu, Ser, and Tyr. Amino acid that are encoded are listed below corresponding codons.