The genetic message in DNA is coded in the bases, grouped in threes. The sequence A-G-C (shown as codon) tells the protein-synthesizing machinery to add a serine to the growing chain. The T-T-G that follows is a triplet code, or codon, for leucine; and G-A-C is the codon for aspartic acid. In this way the amino acid sequence of every protein in a living organism is stored in its DNA.