Caption

DNA molecules. Computer artwork of molecules of deoxyribonucleic acid (DNA). DNA is composed of two strands twisted into a double helix. Each strand consists of an outer sugar-phosphate backbone (thicker tubes) with nucleotide bases attached (tubes inside helix). There are four different bases: guanine, cytosine, thymine and adenine. Guanine always pairs with cytosine and adenine always pairs with thymine. DNA contains sections, called genes, which encode the body's genetic information. Genes determine each cell's structure, function and behaviour.