Crime is as old as human civilization. But so is man's ingenuity in investigating crime. About 150 years ago, fingerprints were used for the first time by a British Administrator, Sir William Herschel, in order to prevent large-scale swindling of funds by illiterate military soldiers. He asked them to put their fingerprints on a piece of paper without knowing its implications. That, however stopped the swindling of funds.
What is DNA fingerprinting?
The chemical structure of everyone's DNA is the same. The backbone of the double-stranded DNA is made up of sugar and phosphate. The two strands are held together by four basic units called bases, adenine, thymine, guanine and cytosine. Each and every person has a different sequence owing to the presence of millions of base pairs in each person's DNA. These sequences are responsible for the identification of a person. However, because there are so many millions of base pairs, scientists use a shorter method, based on repeating patterns in DNA.
A class of repetitive DNA such as GATA repeats is differently organized in different individuals. The technique by which we can detect the variation in copy number between individuals is called DNA fingerprinting. This nomenclature was used by Alec Jeffreys to emphasize that DNA pattern of each individual is as unique as are our fingerprints. In fact, our DNA fingerprint patterns are much more unique compared to our fingerprints.
There may be certain bands common in some individuals, but one can never get all the bands exactly the same as in another individual, except identical twins who will have identical DNA fingerprinting pattern. These bands are, therefore, used in forensic investigation. For example, in a family consisting of father, mother and a child, if one conducts DNA fingerprinting test, the pattern in each individual looks very different. However, when one looks very carefully, every band present in the child is accounted for, either being present in the mother or in the father. There will not be any band present in the child that is not present in either parent. In the case of brothers and sisters, however, DNA fingerprinting patterns will not be identical. They will be different.
Applications of DNA fingerprinting
DNA fingerprinting is finding extensive use in innumerable areas.
1. Crime investigation: in cases of rape, murder assassination, theft, etc.
2. Authenticity of consumer products: Quite often fake goods are marked in the name of reputed companies. In order to protect their credibility, many of these top-ranking companies put DNA samples of known DNA sequence underneath each label stuck on each manufactured item. If suspected, these labels can be removed and DNA sequence can be decoded, which helps in the authentication of the product.
3. Medical diagnosis: In certain diseases such as leukemia, DNA fingerprinting pattern of blood is drastically different compared to the parents of the individual. In such cases, DNA fingerprints can be taken as a signal for identifying the diseases.
4. Pedigree analysis: Extensively used in horse, cattle and buffalo breeding programmers. There are people who are ready to pay much larger amounts for high pedigree breed known to yield higher quantity of milk, disease-resistant or a much faster runner. It also is used for determining the pedigree of dogs.
5. Seed-stock identification: Used for patenting varieties developed by scientists and released to the farmers. The probability of another scientist developing similar varieties independently having identical DNA pattern is virtually nil. It is also used in molecular breeding of plants.
6. Sex-selection in animals: Y chromosome-specific STR markers are used for determining the sex .It is also possible by using FACS to sort Y-bearing sperms from the X-bearing sperms and use them insemination and production of animals of desired sex.
7. Defense records: In US, blood samples of newly recruited soldiers are stored in a freezer. During war when a soldier goes missing, and a mutilated body is discovered and a mutilated body is physically impossible to identify the body, DNA isolated from the suspect's blood samples stored earlier is compared with that from the mutilated body to establish identity.
8. Family matters: Used in establishing paternity or maternity, identity of a missing child and in cases of exchange of babies in maternity wards.
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