Genetic testing. Sterile cotton swab inside a sample tube, next to a DNA autoradiogram film. The swab is used to collect a sample of cells from the lining of the mouth. DNA (deoxyribonucleic acid) is extracted from the cells and analysed to determine the genetic sequence (shown by the autoradiogram). Genetic testing may be used to establish paternity, to identify criminals or to determine if someone is predisposed to a disease.