A method of DNA fingerprinting that is especially useful for analysing samples of DNA where there is little or no knowledge of the organism’s genome. It is often employed to determine if two organisms, e.g. two bacterial samples, belong to the same species. Other uses include tracking genetic variation in populations and forensic analysis of human DNA. Essentially the DNA sample is digested with particular restriction enzymes (see restriction fragment length polymorphism) and the resultant restriction fragments are incubated so the ends join to specially designed adaptor sequences. A selected subset of the DNA fragments then undergoes amplification via the polymerase chain reaction, and the amplified fragments are separated by gel electrophoresis according to their size and electrical charge. This creates a pattern of bands characteristic for the original DNA sample.