Genetic fingerprinting has changed the course of crime detection. It is the most accurate method yet developed of identifying individuals. The probability against any two genetic fingerprints being the same by pure chance is greater than the number of people on Earth. The technique can also prove paternity of children and is being used to control the breeding of rare animals.
Professor Alec Jeffreys, a British geneticist at Leicester University, discovered genetic fingerprinting in 1984. He was conducting research into DNA – the chemical substance in the nucleus of every living cell which determines a person’s individual characteristics, such as the colour of hair and eyes. The structure of DNA is different in everybody, with the exception of identical twins.
Professor Jeffreys discovered that within the DNA molecule there is a sequence of genetic information which is repeated many times along the structure of the DNA, which looks like an endless twisting ladder.
The length of the sequence, the number of times it is repeated and its precise location within the DNA chain are unique to each individual. A process was developed to translate these sequences into a visual record. The finished picture, the genetic fingerprint, is a series of bars on an X-ray film, rather like the bar codes printed on food packets.
To obtain a DNA specimen, a scientist only needs a biological sample containing some human cells. This is usually blood, semen or hair, and only very small amounts are necessary.
Genetic fingerprinting is an important in establishing innocence as guilt. For example, a burglar who breaks a window may leave a blood sample behind on the glass. This can be used to create a genetic fingerprint. When police arrest a suspect, a blood sample can be taken from him and compared. If it matches, he is the burglar. If it does not, he is innocent.
When the police have a genetic fingerprint, but no suspect, they can fingerprint groups of people by taking samples of their blood. The first mass genetic fingerprinting happened in Leicestershire in 1987 when samples were taken from 5500 men living around a village where two young girls had been raped and murdered.
The killer was eventually found when a man was heard to say that a workmate had asked him to take his place when the samples were being taken. Another man who had previously been accused of one of the murders was freed because his genetic fingerprint did not match those made from the scene-of-crime evidence.
Genetic fingerprinting can also determine who is the father of a child and resolve paternity disputes. A DNA strand is made up equally of the characteristics of each parent. By comparing the genetic fingerprints of mother and child, a scientist can say with certainty that the parts of the child’s fingerprint which do not match those of the mother must have come from its true father.
Another use is in bone-marrow transplants which are given to people suffering from leukaemia. Doctors can check whether the genetic fingerprint extracted from a patient after a transplant matches that of the donor. If it does, the transplant has been successful and is producing healthy white blood cells. If it does not, the transplant has failed to take. This allows the possibility of another transplant.
Zoologists can use genetic fingerprinting to control the breeding of rare animals and preserve species. They can compare genetic fingerprints taken from animals to ensure that inbreeding among endangered species, which is known to lead to weaker animals, is avoided.
Picture Credit : Google