DNA analysis, negative image. Petri dish with the letters DNA, test tubes and eppendorf tubes containing samples of DNA (deoxyribonucleic acid) on graphs 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 finding the function of genes.