As fingerprints have proved useful for identification of individuals to fairly good extent, DNA of an individual distinguishes her or him more exactly from others and using DNA for distinguishing and identification is DNA fingerprinting.
DNA Fingerprinting (DNA Profiling) Principle:
- It is a quick way to compare the DNA sequences of any two individuals. It is also known as DNA Profiling
- Prof. Alec Jeffreys developed the technique of DNA fingerprinting in an attempt to called as repetitive DNA. The repetitive DNAs are separated from bulk genomic DNA as different peaks during density gradient centrifugation. The bulk DNA forms a major peak and the the other small peaks are referred as satellite DNA.
- Satellite DNA can be classified as micro satellites, mini satellites etc., bases on the length of segment and number of repetitive units. These sequences show high degree of polymorphism and form the basis of DNA fingerprinting.
- DNA profiling uses repetitive (repeat) sequences that are highly variable, called VNTRs (Variable Number of Tandem Repeats) or Mini Satellite, particularly short tandem repeats (STRs).
- PCR (Polymerase Chain Reaction) technique can be used for DNA profiling. It can be used to amplify the tiny amount of DNA into amounts that are large enough for detection.
DNA Fingerprinting Steps Involved
1. A drop of blood or semen or a piece of hair root or any tissues can be used to isolate DNA. Extract and purify DNA from cells.
2. DNA is digested or restricted with restriction endonucleases without causing cut in the minisatellite region
3. DNA fragments are separated by gel electrophoresis.
4. Separated DNA fragments are transferred to nitrocellulase membranes.
5. Add labeled VNTR probe for hybridization to take place
6. Wash off unbound probe.
7. Hybridized DNA fragments are detected by autoradiography.
Applications of DNA Fingerprinting
1. It is the basis of paternity testing in case of disputes.
2. It is useful as identification tool in forensic applications.
3. Diagnosis of Inherited Disorders
4. Developing Cures for Inherited Disorders By studying the DNA fingerprints of relatives who have a history of some particular disorder
5. To confirm cell line identity in a cell line collection.
6. To assess migration pattern of ancient populations.
7. It is used in determining population and genetic diversities and also in evolutionary biology. Pedigree analysis in man, dog, birds etc