Caption

DNA molecule. Computer artwork of the structure of deoxyribonucleic acid (DNA). DNA is composed of sugar (yellow), phosphate (pink), oxygen (red), hydrogen (black), nitrogen (blue) and nucleotide bases (green and orange). The sugar and phosphate form two strands, which twist to form a double helix (not seen). Each sugar has a nucleotide base attached to it. There are four bases: guanine (G) and adenine (A) (purines, orange), and cytosine (C) and thymine (T) (pyrimidines, green). The bases link together in the centre of the double helix using hydrogen bonds (grey lines). T always links with A, and C always links with G. DNA contains an organism's genetic information.