Codon Usage Bias Measured Through Entropy Approach

Codon usage bias measure is defined through the mutual entropy calculation of real codon frequency distribution against the quasi-equilibrium one. This latter is defined in three manners: (1) the frequency of synonymous codons is supposed to be equal (i.e., the arithmetic mean of their frequencies); (2) it coincides to the frequency distribution of triplets; and, finally, (3) the quasi-equilibrium frequency distribution is defined as the expected frequency of codons derived from the dinucleotide frequency distribution. The measure of bias in codon usage is calculated for 125 bacterial genomes.