Papers in the Biological Sciences



Codon Usage

Date of this Version

January 2003


Published in Encyclopedia of the Human Genome. Copyright © 2003 Macmillan Publishers Ltd, Nature Publishing Group / Used by permission.


The genetic codes have degeneracy; that is, most amino acids (18 out of 20 in the universal genetic code) are encoded by more than one codon. Codons encoding the same amino acid are called synonymous codons. Both in prokaryotic and eukaryotic genes, the synonymous codons are not used with equal frequencies.