The genetic code is thought to have evolved to maximize genetic stability by minimizing the effect on protein function of most substitution mutations (single-base changes). We will use the six arginine codons to test this idea. Consider all of the substitutions that could affect all of the six arginine codons.
(a) How many total mutations are possible?
(b) How many of these mutations are "silent," in the sense that the mutant codon is changed to another Arg codon?
(c) How many of these mutations are conservative, in the sense that an Arg codon is changed to a functionally similar Lys codon?