Features of Recent Codon Evolution: A Comparative Polymorphism-Fixation Study

Figure 2

Normalized difference of codon changes (gain and loss) at the polymorphic and fixed sites in amino-acid coding regions. The normalized difference of a codon was defined as the difference of the number of mutations removing the codon from that creating the codon and divided by the total number of mutations in the codon. Codons are ordered (left: ancient; right: recent) in their temporal order in the genetic code according to Trifonov [2]. The codons associated with codon capture are in lower case.