DNA fingerprinting is the technique of finding the difference between the satellite DNA regions in the genome. These regions are stretches of repetitive DNA which do not code for any specific protein. These non-coding sequences form a major chunk of the DNA profile of humans. They depict a high level of polymorphism and are the basis of DNA fingerprinting. These genes which show a high level of polymorphism in all kind of tissues as a result of which they prove to be very useful in forensic studies. Any piece of DNA sample found
Any piece of DNA sample found at a crime scene can be analysed for the level of polymorphism in the non-coding repetitive sequences. After the DNA profile is traced, it becomes easier to find the criminal by performing the DNA fingerprinting for the suspects. Apart from crime scenes, Fingerprinting applications also prove useful in finding the parents of an unclaimed baby by conducting Paternity test on a DNA sample from the baby.
Alec Jeffreys developed this technique in which he used a satellite DNAs also called VNTRs (Variable Number of Tandem Repeats) as a probe because it showed the high level of polymorphism. The process includes
- Isolating the DNA.
- Digesting the DNA with the help of restriction endonuclease enzymes.
- Separating the digested fragments as per the fragment size by the process of electrophoresis.
- Blotting the separated fragments onto synthetic membranes like nylon.
- Hybridising the fragments using labelled VNTR probes.
- Analysing the hybrid fragments using autoradiography.
As discussed earlier the technique of fingerprinting is used for DNA analysis in forensic tests and paternity tests. Apart from these two fields, it is also used in determining the frequency of a particular gene in a population which gives rise to diversity. In case of the change in gene frequency or genetic drift, Fingerprinting can be used to trace the role of this change in evolution.
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