Comparitive Study of DNA Fingerfprinting of Biological samplies obtained from Crime Scene using AFLP Methods

Author Name(s): Tara abdul rehman
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The use of DNA finger printing technology in the area of crime investigation and individual identification has gained tremendous importance. These are several techniques like AFLP, RFLP, RAPD, VNTR and others which will help to analyze the variations among the test samples based upon the type of fragmentation seen and the band pattern observed. The current work is related to the application of the techniques like AFLP an RFLP in the field of Forensic investigation by individual identification. The current work involves the collection of the various biological samples from the assumed crime scene followed by the use of AFLP technology to digest the samples. This step can be preceded by the separation of the fragmented DNA of both test and the standard samples on the Agarose gel thereby observing the band pattern after agarose gel electrophoresis. The main objective of the study is to compare DNA fingerprints of different DNA samples extracted from various biological sources like hair follicle, blood cell, tooth using the polymorphism in RFLP regions and AFLP to finally establish if they are from the same individual.


DNA Finger printing, AFLP, RFLP, VNTR and RAPD


DNA Finger printing is a method of identifying the uniqueness in the samples based on the band patterns obtained after the process of restriction digestion of the samples. The DNA of each individual differs from the other with respect to the junk DNA or heterochromatin. It is this DNA that makes a unique Finger print pattern on gel electrophoresis.
There are certain repeats like STR’s, VNTR’s etc that would be present at different sites in different numbers among different individuals. Based upon the presence of these patters each individual differs from the other in their DNA Fingerprinting.
DNA fingerprinting has been accepted in most courts in the United States, and has in several notable instances been used to exonerate or free persons convicted of crimes, but the Supreme Court has ruled (2009) that convicted criminals do not have a constitutional right to DNA testing [1] There are several techniques within the DNA Fingerprinting method like VNTR, AFLP, RFLP etc. VNTR infers variable number of tandem repeats which are the repeats that are present at variable regions within the DNA. These regions have specific sites that can be digested by specific restriction enzymes. These sites can be used in the individualization of the DNA samples based on their restriction pattern. The probability of matching VNTR pattern between two individual is very much rare as it may occur in one person within twenty billion of people [2]. VNTRs are the result of genetic heritability. AFLP’S refers to the polymorphism observed in the band size of the amplified DNA fragments which is caused due to the presence of SNP’s Single Nucleotide Polymorphisms. The AFLP technique is based on the selective PCR amplification of restriction fragments from a total digest of genomic DNA [3] DNA Finger printing van be infrerred as a process used in the identification of the individual when an attacker or assailant has left some kind of bodily fluid or blood at the scene of a crime and when no visual identification is possible [4]. Not only in the Forensic identification but DNA Fingerprinting is also employed in describing the populations of several phytonematodes, including the pinewood, burrowing, root-knot, and cyst nematodes [5].


From the results of restriction Digestion and AFLP analysis it can be concluded that the DNA fingerprints obtained from different individuals do vary in the number and size based on the AFLP sites present. This fact can be of extensive use in the identification of criminals from the DNA obtained at the crime scene. In the current work a total of 4 samples were collected one among which is from the assumed crime scene.
The other 3 samples correspond to the 3 suspects. Upon the analysis of AFLP band patterns it can be inferred that out of the three suspects the suspect sample 2 matches the band pattern of the sample obtained from the crime scene. This confirms that the DNA obtained at the crime scene is the sample of the suspect 2.
The main objective of the work is to highlight the importance of the AFLP methodology in the field of individual identification.

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