Forensic Individualization of Suspected Criminals using Apolipoprotein B (APoB) Hyper Variable Region

Author Name: *Md Shahbaz Alam,A.K Gupta,Archana Tripathi
Author Email: kshindwi@gmail.com

Abstract

In forensics, DNA has been used to sort out the problem related to personal identification for over three decades with absolute accuracy. In this study an attempt has been made to isolate DNA from exhibits like Cigarette butt, Handkerchief and scalp hair collected from crime scene and subsequently the control samples were taken from the suspects. The isolated DNA was amplified by using universal APoB primer, resulting in the formation of band pattern which was helpful in interlinking the suspects with assassination. The present study concludes that the exhibits collected from crime scene containing sweat and saliva even in trace amount and hair can be used as reliable source for individualization using VNTR based DNA typing.

Keywords

Forensic Science, DNA isolation, Polymerase chain Reaction, variable number of tandem repeats, APoB primer, Hyper Variable Region

Introduction

It has been evident that Variable Number of Tandem Repeats (VNTRs) are highly polymorphic markers[1-3].Each VNTR locus is associated with a large number of different allele, each allele corresponding to a specific number of repeated sequence in any population. Each individual carries two alleles only –one on each of two homologous chromosome. The important methodological merit of VNTRs is its unique pattern for every individual.
Due to highly polymorphic character VNTRs are used as an important tool in forensic identification and comparison. They also constitute preferred system for ‘DNA Fingerprinting’, the direct practical application of which includes criminal and forensic examination, in solving the problem of identification amongst a large number of suspects.DNA isolated from biological materials can be analyzed by DNA Profiling to help establish the source of deoxyribonucleic acid (DNA) [7-8]. It has been demonstrated many time that blood, semen, hair root, tissues, bone are good source of DNA for identity testing [9-11]. Sweat is also a useful material in this respect. These biological materials recovered from crime scene rely primarily upon the identification of blood group, antigens and rarely on iso-enzyme and polymorphic protein. These approaches have several inherent limitations, especially their limited detect-ability because of the low concentrations of antigens, isoenzymes and proteins in the samples. In addition to these, drying, aging, and contamination associated with the samples limit the number of markers that can be typed. The potential for discrimination using these markers are also less sensitive than DNA analysis.
The study performed by Tamer et al [12] estimated the frequency of APoB point mutations in 179 atherosclerotic, 145 hyperlipidaemic Individuals and 272 healthy individuals in the east Mediterranean region of Turkey. Lipid and lipoprotein level were measured with routine biochemical analysis and APoB mutation was detected using realtime PCR. In this region, APoB mutation was observed as rare causes of hyperlipidaemia and atherosclerosis may therefore be unrelated to them. Dekha et al [13] reported the allele frequency distribution at the hypervariable locus 3′ to the apolipoprotein B gene (ApoB 3′ VNTR) in five well-defined human populations by using the PCR technique. A total of 12 segregating alleles were detected in the pooled sample of 319 individuals. A fairly consistent pattern of allele frequency distribution was found apparent in most of these geographically and genetically diverse populations, suggesting that the ApoB 3′ VNTR polymorphism predates the geographic dispersal of ancestral human populations. In spite of the observed high degree of polymorphism at this locus, the genotype distributions in all populations confirm to their respective Hardy-Weinberg predictions. The result also shows that alleles that are shared by all populations have the highest average frequency within populations. The APoB gene contains a hypervariable region consist of VNTRs DNA sequences. They suggested a general method for amplification of targeted VNTR region.
These findings demonstrate the potential utility of highly informative hypervariable loci such as the ApoB 3′ VNTR locus in population genetic research.
Now a days the criminals are active and aware about the evidence which normally left at the scene of crime during committing a crime, but they unknowingly and hurriedly leave some physical / biological evidence at crime scene. The major challenge for forensic scientist is to isolate DNA from such evidences containing trace amount of biological materials.
It is necessary to use a suitable and appropriate method for extraction and isolation of DNA from different biological sources using reliable methods, because once the sample are utilized wrongly it can’t be used again .The DNA sample are very much sensitive to cross contamination, hence the use of appropriate primer for DNA typing is necessary to form a definite interpretation of result.
In the present study, DNA extracted from saliva and sweat suspected over cigarette butt and handkerchief, as well as from hair root meshed in the fist of victim. VNTR studied in this report is present at 73 base pair (b.p) 3’ to the second polyandenylation signal of the human ‘Apolipoprotein B, (APoB) gene (which is located on chromosome 2) and is commonly referred to as APoB 3’HVR (Hyper Variable Region) [4-6].APoB 3’-HVR alleles and genotype have been much studied in numerous population. The banding pattern obtained has been utilized in identification of culprit involved in the murder case.

Conclusion

APoB is a universal marker found in almost every individual but with different base pair length .In the present study APoB marker was used to solve a murder case which gave a trustworthy result. From this study it was concluded that APoB locus can be used in forensic science for identification of criminals in almost every cases.

16 total views, 0 views today

Download File

About the author: tej