DNA finger printing or DNA profiling is generally used for the identification of criminals from bloodstains semen etc. and for establishing parentage in cases of dispute. The data from this approach are extremely reliable as compared to the conventional analysis of serum proteins and erythrocyte antigens and proteins.

DNA fingerprint of an individual is essentially a southern blot of his DNA digested with an endonuclease and probed with a radioactive DNA probe. The procedure for DNA finger printing is briefly described below.

The first step to obtain a sample of DNA of the individual in question. The DNA is usually obtained from blood samples, but it may be isolated from several years’ old blood or semen stain on clothing’s, from vaginal swabs taken from rape victims, even from bone marrow of years old bones of murder victims, etc. The amount of DNA needed for developing fingerprints is very small.

DNA is digested with suitable restrictions endonuclease and the digest is subjected to get electrophoresis.

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The DNA is denatured and then transferred from the gel into nitrocellulose filter membrane, where it is fixed by backing the filter at 80 degree Celsius.

The DNA as the filter is hybridized with the appropriate radioactive probe (single standard DNA probe), the free probe is washed off as the bonds to which the probe has hybridized are detected through autoradiography.

The probes used for DNA finger printing are usually prepared from minisatellite or micro-satellite DNA. The minisatellite DNA is highly variable mainly due to variation in the number of tandem repeats of a short care sequence i.e., GGAGGTGGGCAGGAG (or A) G.

Some examples of such probes are, probe 33.61 (AGGGCTGGAGG) 3.18 probe 33.15 (AGAGGTGGGCAGGTGG) 29, and probe 33.5 (GGGA (or C) GTGGGCAGGAGG) 14.

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These probes hybridize, under conditions of low stringency to a number of polymorphic loci represented by ministringency DNA.

A simple universal probe, a tender repeat of GATA, has been developed from the sex chromosomes of bonded krait, this probe is repeatedly very useful in DNA finger printing of not only man but of many other organisms, including plants. The bonds appearing in DNA finger print of the suspected criminal are compared with those obtained from test DNA recovered from the evidence for crime and believed to originate from the criminal e.g., semen stains or sperms nuclei in virginal swabs from rape victim, etc.

There should be a perfect match in case the suspect had been involved ordinarily a molecular weight marker lane is run and some related and unrelated control samples are also included. In case of disputed parentage, the DNA fingerprints of the child, the mother and the suspected father are compared. As a rule the bonds present in a child’s fingerprint must be accounted for by those in the mother’s and the father’s finger prints. Therefore, the child fingerprint is compared with that of mother and their common bonds are marked. The remaining bonds in the child’s fingerprint must be present in that of child’s father.

In medicine, DNA finger printing application in genetic counseling tracing the frequency of door cells in bone marrow transplants, tissue culture cell line identification etc.

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In case of animal husbandry, proofs of parentage poaching identification in case of theft or loss, detection of trait markers are the areas of application. Similarly, identification of plant varieties for patent, parentage and trait market purpose and of microorganisms strains is unequivocal with DNA finger printing.