Genetic fingerprinting

Fingerprints are unique to each individual. Methods of recording and matching fingerprints have allowed police to correctly identify many criminals. Genetic scientists have recently developed another tool for identification based on the uniqueness of each person's genes.

Genetic differences between people account for the large variations we see among individuals. Each human has approximately 100,000 genes in the chemical form of DNA. No two humans, except for identical twins, have exactly the same genetic code . A description of a person's DNA that is detailed enough to distinguish it from another person's DNA is called a DNA or genetic "fingerprint."

History

In 1984 English researcher Alec Jeffreys developed a technique to display a person's genetic code as an X-ray picture of bands of dark and light. These bands were the result of attachment of radioactive segments of DNA to certain sites on the DNA fragments, creating a unique pattern for the individual. This direct DNA analysis revealed so much variation in the genetic code between different people that even a small section of the entire genetic code could identify an individual's special combination of traits.

Erlich's Method

Three years later, Henry Erlich developed a method of DNA finger-printing so sensitive that it could be used to identify an individual from an extremely small sample of hair, blood, semen, or skin. Erlich's technique used Jeffreys' traditional method and combined it with a new technique called polymerase chain reaction (PCR).

Using his new method, Erlich was able to duplicate and heat-separate the DNA fragments from a single human hair root many times. The amplified DNA was then used to obtain a DNA fingerprint.

Applications

Genetic fingerprinting has already proved to be a very useful tool. Initially, it was used exclusively in forensic (criminal) science and law. This technique has helped to link suspects to crimes where a single drop of blood was the only clue. When there is a need to know who an individual's biological mother or father is, genetic fingerprinting can provide the answer by matching DNA elements between parent and child.

DNA fingerprinting must be done with great care, however, since any contamination of blood samples by mixing them or touching them with ungloved hands, etc., can produce false results, with serious consequences in legal proceedings, such as a trial. If carefully done, however, genetic fingerprinting can provide accurate identification of an individual.