DNA analysis. Graphs showing the results of DNA (deoxyribonucleic acid) sequencing twisted into a helix. 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.