Genetic sequence. Computer illustration of a sequenced section of DNA (deoxyribonucleic acid). DNA contains the genetic code as a sequence of four molecules called nucleotide bases: adenine (A, green), cytosine (C, blue), guanine (G, black) and thymine (T, red). The sequence is also represented as a graph below the corresponding set of letters. DNA encodes, transmits and controls the development of the hereditary traits of living organisms. The sequence was produced by the automated separation of a sample of fragmented DNA.