Number of extremely biased codons (“zero-codons”) found in DC and NDC tissue-specific genes across mammals.

Table 1 shows the number of extremely biased codons (“zero-codons”) in gene tissues and across mammals. Genes are grouped in DC and NDC. The number of “zero-codons” is based on codons usage (CU) value that we calculated in each group of genes and across mammals. The DC genes retain a multiple codon usage (low CUB), therefore with a few “zero-codons” compared to NDC genes. Notably, the number of “zero-codons” is much higher in muscle and kidney NDC and skin DC genes, therefore with a disease-driven behavior. CUB increased progressively during evolution, although not at the same extent in all gene groups. The most remarkable difference in the “zero-codon” number is between HSA kidney DC (11) and NDC (94) genes and muscle DC (49) and NDC (109) genes.