A codon chart, also known as a base pairing table, is a tabular representation of the genetic code that shows which three nucleotides in DNA represent a specific amino acid. The diagram on the left is an example of this type of diagram. Codon charts were originally drawn one letter to one amino acid; there are now six possible combinations for each three-letter codon sequence. The key on the lefthand side displays all 64 possible patterns that the four letters can take in a four-square matrix: A-, T-, C-, G-.
The following is an example:
Either GCG or GGC give rise to serine, and either CAT or ATC gives rise to proline.