Tri-allelic pattern at the TPOX locus: human identification in Brazil

Abstract

Introduction: Polymorphic short tandem repeats (STRs) are powerful genetic markers to distinguish individuals and still preferred for forensic applications and relationship testing. Tri-allelic pattern may have several causes, such as chimerism or chromosomal mutations. Objective: This paper reports a tri-allelic pattern at the TPOX locus, which was encountered in our laboratory during analysis of an item from an attempted murder case. Materials and methods: DNA extraction was the organic method with alcoholic precipitation. Real Time PCR quantified DNA samples, with the use of the reagent Quantifilier® TRIO DNA Quantification Kit. PCR analysis system approached by STRs IdentiFiler® and Capillary electrophoresis procedures were performed on the ABI 3500 Genetic Analyzer. Results: This is the first report about tri-allelic pattern by forensic analysis in Brazil Northeast region. In the course of routine multiplex PCR-based forensic testing using microsatellite markers in the IdentiFiler® kit, we have found one case where the analysis pattern of one of the loci has yielded three peaks instead of the normal one or two. Conclusions: The examination indicated the presence of tri-allelic pattern which indicates a standard tri-allelic type 2. Further, it is likely that powerful, high throughput genotyping methods will be applied in forensic testing in the future.