Measures of Relative Codon Biases
CAI: codon adaptation index
This specifies a reference set of genes, almost invariably, H, chosen from among “highly expressed genes.”
Defining W(xyz) = f(xyz)/max(xyz[a])*f(xyz,H) as the ratio of the frequency of the codon (xyz) to the maximal codon frequency in H for the same amino acid a ,the CAI of a gene of length L is taken as PI(Wi)^(1/L) (the log average), where i refers to the ith codon of the gene and w is calculated as above.
H 集合是所选择的高表达量的参考基因