Question

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.Part A How many total mutations are possible?Part B How many of these mutations are "silent," in the sense that the mutant codon is changed to another Arg codonPart C How many of these mutations are conservative, in the sense that an Arg codon is changed to a functionally similar Lys codon?

Answer 1

The six codons for arginine are the following:

GCA, GCG, GCT, GCC, TCT, TCC

A) Considering the individual bases in each codon, three mutations are possible at each base position. Hence, 3 × 3 × 6 = 54 mutations are possible.

B) Considering the mutations at the 3rd base: 3 × 4 + 1 × 2 = 14 of these mutations are silent mutations.

C) Lysine codons are the following:

TTT, TTC

There are two possible mutations that can give a lys codon.

Hope that answers the question, have a great day!