Table 2.

Effects of a single codon residue on the structure of the amino acids.

The 16 amino acids coded by symmetric codons were sorted into rows accordingly to their central codon residues (_A_: adenine, _U_: uridine, _C_: cytosine and _G_: guanine) and into columns accordingly to their 1^st and 3^rd codon residues (U_U, A_A, G_G, C_C). The 4 amino acids coded by only asymmetric codons are also included into the table (last columns). Some structural features in the amino acids could be related to the central codon residues (atoms in grey boxes and the yellow column in the middle of the table).