Codon volatility is defined as the proportion of non-synonymous mutations among the codon's point-mutation neighbors. The synonymous codons of some amino acids, e.g. serine or leucine, differ in their volatilities. It has been suggested that preferential usage of volatile, resp. less volatile codons, can be interpreted as a sign of selection. The student will summarize the literature on the relationship between codon volatility and selection, and also test the hypothesis that at functionally important protein sites, less volatile codons are used because they minimize the probability of a non-synonymous, deleterious mutation. The hypothesis will be tested by computer simulations, as well as analysis of real data.
