Computer graphics image of DNA, showing its double helix structure. The DNA molecule's atoms are colour coded: carbon atoms are dark blue, nitrogen lighter blue, oxygen red, phosphorus green. DNA (deoxyribonucleic acid) consists of two linked strands of nucleotides, coiled into a helix. The strands are joined by the pairing of organic bases on adjacent nucleotides. Each nucleotide contains the sugar deoxyribose & one of four bases: thymine (T), adenine (A), cytosine (C), guanine (G). T pairs up only with A, C with G. The genetic information is determined by the order of the pairs. The image shows the B form of DNA (B-DNA).