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Forensic mitochondrial DNA analysis

Abstract:

The introduction of mitochondrial DNA (mtDNA) investigation in forensic genetics allowed to obtaining results from ancient, residual and degraded samples, enlarging extensively the possibility of applying genetic analyses to difficult forensic cases. However, the particular characteristics of mtDNA brought some conceptual and statistical challenges to forensic genetics, namely: the uniparental (maternal) transmission implies lineage instead of individual characterization, so that mtDNA can be more informative in excluding rather than in including a suspect; the absence of recombination in mtDNA renders impossible to apply the product rule for estimation of match probabilities, so that evaluations are limited to the frequency of a certain haplotype in a database; most of mtDNA haplotypes are unique or very low frequent, implying that databases must have a considerable number of individuals in order to be informative; heterogeneity in mutation rates between mtDNA positions and heteroplasmy must be taken into account when evaluating if diverse haplotypes can come from the same individual. Typically, the mtDNA survey in forensic genetics is performed by sequencing two hypervariable regions in the control region or D-loop. Some databases, reporting haplotypes in diverse populations, are publically available for forensic purposes. Recently, information from other polymorphisms located in the coding region is being also added to forensic analyses, which allows to inferring more securely the haplogroup to which the haplotype belongs. This phylogenetic information can be very informative for quality purposes, helping in detecting possible mix-up of samples and in checking haplogroup defining polymorphisms. Lately, the mtDNA screening is being enlarged to the total control region (~1200bp), and in the near future to the complete molecule. Such amount of information, in such a short period of time, will challenge forensic genetics in maintaining its strict quality-control of sequences and in being efficient to updating online databases for match evaluation. © 2010 Nova Science Publishers, Inc. All rights reserved.