DNA fingerprinting is a method used to identify an individual from a sample of DNA by looking at unique patterns in their DNA.
- DNA fingerprinting was invented in 1984 by professor Sir Alec Jeffreys.
- Almost every cell in our body contains DNA, on average about 99% of DNA between two humans is the same.
The remaining percentage is makes us unique. Although this might sound like a small amount, it means that there are around three million base pairs that are different between two people.these differences can be compared and used to help distinguish one from other.
The technique uses for DNA fingerprinting :-
Alec Jeffreys used a satellite DNA as probe that shows very high degree of polymorphism.
DNA from every tissue such as blood, hair, skin, bone, saliva, sperm etc. from individual show the same degree of polymorphism, they become very useful identification tool in forensic applications.
- A satellite DNA as probe was called as VNTR ( Variable Number of Tandem Repeats).
- The technique as use earlier , involved southern blot hybridisation using radiolabelled VNTR as a probe.
It included –
- Isolation of DNA.
- Digestion of DNA by restriction endonucleases enzyme.
- Separation of DNA fragments by electrophoresis.
- Transferring ( blotting) of separated DNA fragments to synthetic membranes such as nitrocellulose or nylon.
- Hybridisation using labelled VNTR probe.
- Detection of hybridised DNA fragments by autoradiography.
VNTR (Variable Number of Tandem repeats) :-
It belongs toa class of satellite DNA referred to as mini satellite.
- A small DNA sequence is arranged tandemly in many copy numbers, the copy number varies from chromosome to chromosome in a individual. The numbers of repeat show very high degree of polymorphism. As a result the size of VNTR varies in size from 1 to 20 kb.
Applications of DNA fingerprinting :-
- DNA fingerprinting is widely used to find out the real biological parent or offspring in paternity- maternity.
- It is considered to be a sure and best method to identify the real culprit involved in crimes such as murder, rape etc.
- It is also use to find to the original background and historical migration of a particular racial group.
- It also its application in gene therapy as it helps to provide information regarding some specific alleles.