DNA autoradiogram and codons. Conceptual computer artwork of a DNA autoradiogram (yellow) with superimposed triplets of letters (white). An autoradiogram (also known as a genetic fingerprint) consists of several columns of bands that show a specific sequence of nucleotide bases. Bases are the genetic code parts of DNA (deoxyribonucleic acid) and there are four bases: adenine, guanine, cytosine and thymine. The bases are read in groups of three called codons. GAC (guanine adenine cytosine) codes for the amino acid aspartic acid, for example. When one codon is read, its amino acid is added to the chain of amino acids from previous codons, which forms proteins.