Caption

DNA molecules. Computer artwork of molecules of DNA (deoxyribonucleic acid). DNA is composed of two strands (outside) twisted into a double helix. Each strand consists of a sugar-phosphate backbone attached to nucleotide bases (spheres). There are four bases: adenine, cytosine, guanine and thymine. The bases are joined together by hydrogen bonds (rods between spheres). DNA contains sections called genes that encode the body's genetic information.