What Is DNA Fingerprinting?

Man scanning fingerprint on machine with screen in laboratory
Monty Rakusen/Getty Images

DNA fingerprinting, also known as genetic fingerprinting, DNA typing, and DNA profiling is a molecular genetic method that enables identification of individuals using hair, blood, semen or other biological samples, based on unique patterns (polymorphisms) in their DNA. When first described in 1984 by British scientist Alec Jeffreys, the technique focused on sequences of DNA called mini-satellites, that contained repeating patterns with no known function.

These sequences are unique to each individual, with the exception of identical twins.

Different DNA fingerprinting methods exist, using either Restriction Fragment Length Polymorphism (RFLP) or PCR or both, and targeting different areas of DNA including those with known variations in single nucleotides (single nucleotide polymorphisms; SNPs), short tandem repeats (STRs) and other various repeating polymorphic regions. The odds of identifying an individual correctly depend on the number of repeating sequences tested and their size.

DNA fingerprinting, when used for forensic science, makes use of probes that target regions of DNA that are specific to humans, thus eliminating any possibility of contamination by extraneous DNA from bacteria, plants, insects or other sources.

How Is DNA Fingerprinting Used?

There are quite a few uses for DNA fingerprinting. Here are some of the most common ways.

Forensics: As most TV watchers know, DNA fingerprinting can be accomplished with a very small quantity of DNA, and is a sure-fire way to "finger" a culprit in a crime. Similarly, DNA fingerprinting can and does exonerate innocent people of crimes-- sometimes even crimes committed years ago. DNA fingerprinting can also be easily used to identify a decomposing body.

Non-Criminal Identification: Is Joe really Billy's father? DNA fingerprinting can answer that question quickly and accurately. In addition to identifying adoptive children and settling paternity suits, DNA fingerprinting has also been used to establish a relationship in the case of inheritance. More than once, DNA fingerprinting has made it possible for people separated as a result of natural disaster or war to find their children and parents.

Medicine: DNA fingerprinting serves several uses in medicine. One important instance is identifying good genetic matches for organ or marrow donation. Doctors are also beginning to use DNA fingerprinting as a tool for designing "personalized" medical treatments for cancer patients. In at least one case, DNA fingerprinting was used to ensure that a tissue sample had been correctly labeled with the right patient's name.

Agriculture: All living things have DNA--which means that DNA fingerprinting can be used to identify genetically modified or "heritage" plants, or plants which are likely to have therapeutic value. It can also be used to prove pedigree in valuable animals such as race horses.

How Is DNA Fingerprinting Done?

Typically, for human testing, testers ask the subject for a DNA sample which can be supplied as a blood sample or as a swab of tissue from the inside of the mouth.

A blood sample is usually preferred. Once the sample is obtained and tested, it can be used as a tool for treatment development or compared to that of another person to:

  • Establish a blood relationship between two people
  • Determine whether two people are a good genetic match for medical reasons
  • Determine whether a particular individual's DNA matches DNA at a crime scene
  • Identify a body