Species Identification Through DNA "Barcodes''

Conventional methods for forensic species identification are mainly based on immunological procedures, which have limited applications for old and degraded specimens. The mitochondrial cytochrome b gene sequence has emerged in forensics among molecular methods. Recent investigations in the taxonomic field have suggested that a DNA-based identification system may aid the resolution of animal diversity and classification using sequence analysis and phylogenetic links. Selected gene sequences can be viewed as a genetic "barcode,'' which is enclosed in every cell, and barcoding is a standardized approach for characterizing species using short DNA sequences as a diagnostic biomarker for organisms. The aim of this study was to evaluate the potential of barcode mitochondrial genes, such as the cytochrome c oxidase sub 1 (COI) and the 16S rRNA gene, as a forensic tool. We developed a new approach for species testing and identification with a singleplex PCR amplification that will be useful not only in criminal casework but also in biosecurity, food authentication, investigation against poaching or illegal trade of endangered species, and wildlife enforcement. Seven fragments ranging from 157 to 541 bp (base pairs) in humans were selected from COI and 16S rRNA genes by different redesigned sets of primers suitable for forensic purposes. The specificity of each primer pair was evaluated with a single PCR reaction on different substrates, and the diversity values were calculated by statistical tests to select a set of markers that could be useful in different caseworks. A case example of forensic species identification is also presented.