DNA is referred to as the "genetic code" because it possesses an observable sequence of bases bonded to the sugar phosphate backbone that direct the sequence of amino acids to be used in protein synthesis. This base sequence contains the information necessary to build a protein and is expressed with a four-letter alphabet of bases, which is then transcribed to mRNA and translated into the 20 amino acid alphabet that directs protein synthesis. Because any of the four bases can occur in any order (e.g. A-T, A-G, G-C, etc.), the sequence operates like a code does. Thus, DNA serves as the "genetic code" for an organism, as its base sequence determines its makeup and development.
