DNA analysis, computer enhanced image. Eppendorf tubes containing samples of DNA (deoxyribonucleic acid) on a graph showing the results of DNA sequencing. A DNA molecule consists of two sugar-phosphate backbones, arranged as a double helix, joined by nucleotide bases. There are 4 types of nucleotide base; adenine (A), cytosine (C), guanine (G) and thymine (T). Sequences of these bases make up genes, which encode an organism’s genetic information. Uses of DNA sequencing include finding genes responsible for disease, DNA fingerprinting and paternity testing.