Computer graphics space-filling representation of a section of a DNA (deoxyribonucleic acid) molecule, the genetic material of most living organisms. The double helix of DNA may be regarded as a twisted ladder, the rungs of which are complementary pairs of organic bases: adenine pairs with thymine, cytosine with guanine. It is a precise sequence of DNA bases (a gene), which instructs cells to make a specific amino acid, chains of which form proteins. DNA is the major component of the chromosomes within a cell's nucleus and, through its control of protein synthesis, plays a central role in determining inherited characteristics. DNA computer model in Walter Gilbert's Lab..Human Genome Project.