Using the Jukes-Cantor model, most loci in a genome have a dN/dS ratio

Question

Using the Jukes-Cantor model, most loci in a genome have a dN/dS ratio < 1. This is because most nonsynonymous mutations are deleterious and are selected against.

Quizplus · Accepted Answer

dS is the rate of synonymous mutation (i.e., mutations that do not change an amino acid) and dN is the rate of non-synonymous mutation (i.e., mutations that result in an amino acid change). The mutation rate expected by chance is represented by dS, because synonymous mutations are assumed to be selectively neutral in this model. Most non-synonymous mutations in protein-coding genes are deleterious and are selected against. Thus, dN is usually less than dS and dN/dS is <1 for the majority of loci.

Using the Jukes-Cantor Model, Most Loci in a Genome Have