Ball & stick type model illustrating the structure of the DNA (deoxyribonucleic acid) molecule, the genetic material of most living organisms. DNA consists of a large number of nucleotides joined together in single file to form a strand. Two strands are linked together by base-pairing via hydrogen bonding and coiled into a helix. A nucleotide consists of 3 sub-units: a deoxyribose sugar, a phosphate group & one of four different bases; adenine, thymine, cytosine, & guanine. The former two pair only with each other as do the latter. The genetic information is determined by the arrangement of these pairs along the molecule.