DNA with genetic sequence. Computer artwork of part of a molecule of alpha DNA (deoxyribonucleic acid), the genetic material of all living cells. In the background is a genetic sequence. Alpha DNA spirals anticlockwise when viewed from above. DNA encodes and transmits the hereditary characteristics of living organisms. It consists of two strands wound around each other to form a double helix. The strands each have a sugar- phosphate backbone (blue ribbon) linked by paired nucleotide bases (spheres). There are four bases: cytosine (C), guanine (G), thymine (T) and adenine (A). The sequence of these bases determines each person's unique genetic code.