Human genome. Computer illustration representing the human genome, showing a historical drawing of a man by Leonardo da Vinci, surrounded by DNA genetic sequences. DNA (deoxyribonucleic acid), the genetic material found in all living cells, encodes and controls the hereditary characterist- ics of living organisms. The complete genetic code of each person, their genome, is written as a unique sequence of four nucleotide bases. Each band (white) in the autoradiograms (right) represents the position of one of the bases in the code. At left the code is seen with letters representing the bases: adenine (A), thymine (T), cytosine (C) and guanine (G).