Genetic code. Conceptual computer artwork of a male figure seen against autoradiograms of genetic sequences, representing the genetic code. Each band (blue) on the autoradiograms represents a nucleotide, the chemical unit that makes up DNA (deoxyribonucleic acid). The sequence of nucleotides along a molecule of DNA is known as the genetic code and is unique for every individual. It provides the instructions necessary for the development and functioning of all living organisms. The figure is an anatomical study by the Flemish physician Andreas Vesalius (1514- 1564). Vesalius wrote and illustrated the first comprehensive book on human anatomy, dated 1543.