Caption

DNA helices. Computer artwork of three strands of DNA (deoxyribonucleic acid). Each DNA molecule has a double helix arrangement, being composed of two spiral strands of sugar phosphates. These strands are held together by complementary pairs of four cross-linking nucleotide bases (coloured rods): adenine pairs with thymine, and cytosine pairs with guanine. The order of bases makes up the unique genetic sequence of every individual organism. DNA is found in cell nuclei.