DNA Fingerprinting:
- Human is identified by their names and their characteristic. No two organisms have similar characteristics. (except identical twins).
- There are certain characteristics such as skin colour, hair colour, the colour of pupil of eye, height, voice, a pattern of walking, sitting, way of talking, way of living through which we can differentiate or identify two individuals.
- Every individual differs in fingerprints. There is a difference in imprints and pristine we observe is called fingerprint.
- This is actually an official way of identification of an individual. It was developed by Francis-Galton, which is still in use.
- Alec Jeffreys & colleagues (1985) were investigating a DNA fragment from the gene for a human blood protein, globin.
- They discovered that this fragment contained a sequence of bases repeated several times.
- This repeated DNA is called as minisatellite. Further, the same minisatellite sequence was found in other places in the human genome repeated several times.
- More interestingly, the individuals differ in the pattern of repeats of the base sequence & they differ enough that two individuals have only a remote chance of having exactly the same pattern.
- That means that these patterns are like fingerprints & are called by Jeffreys as DNA fingerprints.
Principle:
- Several small nucleotides are found repetitively in DNA. They are called VNTRs (Variable Number of Tandem Repeats).
- The length to VNTR of two persons may be of the same length but the sequence will be different.
- In every child half of the VNTRs come from mother and other half comes from father.
DNA fingerprinting Technique:
- DNA is isolated from the source material like a drop of blood, saliva, semen, teeth etc. by the help of high-speed Refrigerated centrifuge.
- If DNA is less in the amount it should be amplified using Polymerase Chain Reaction (PCR).
- DNA is cut into fragments using restriction endonuclease enzyme for Restriction Fragment Length Polymorphism (RFLP).
- These fragments are poured into separate wells of an electrophoresis gel and electrophoresed. These fragments are stained with fluorescent dyes like Ethidium Bromide and observed under UV light.
- Alkaline solutions changed this double-strand DNA into single-strand DNA. This process is known as Denaturation.
- The separated DNA fragments are transferred to a nitrocellulose membrane by placing it over the gel. This process is called Southern Blotting.
Application of DNA Fingerprinting:
- In Criminal cases and Family affairs:
- DNA fingerprinting is commonly used in forensic cases to undercover key evidence for criminal trials. In crime scenes, bodily fluids such as blood are taken as samples and tested in a lab to help identify the DNA of individuals who might have contributed or been the victim of the crime. For this technique biological wastes such as blood may be dried, semen, hair, tooth, a piece of bone, anybody tissues etc. is obtained at the site of crime.
- This technique is also used in case of disputed parents where DNA of probable parents are tested against child DNA and help in the identification of actual parents.
- This technique is also helpful in Murder, rape, crime, property nomination, divorce cases. Where the identification of parent is very important. Every individual has received DNA from its parents and can be identified by the help of VNTRs.
Medical Field:
Several hereditary diseases can be detected at the early stage of pregnancy. It can be managed at a certain level through DNA fingerprinting.
- It is used to assess the pattern of migration of ancient populations.
- It is also employed in the genetic analysis of various strains of agricultural crops and animals.
- It is also employed to understand evolution.
