Table 1. Comparison of codon usage between two human genes.

For each codon, we report its absolute frequency of occurrence in each gene and its relative frequency compared with synonymous codons. The P value for each amino acid reflects whether or not the two genes differ in their encoding of the amino acid (Fisher exact test). A complete comparison of all 61 condons is given as Table 2, which is published as supporting information on the PNAS web site. The comparison between these genes is typical of comparisons between other genes from their respective tissues, testes and uterus. Gene A, testis-specific glycerol kinase (GI 516123); gene B, endometrial bleeding factor (GI 2058537).