Development of a nomenclature system for a canine STR multiplex reagent kit.

Despite the popularity of dogs in US households, canine DNA evidence remains largely untapped in forensic investigations partially because of the absence of well-defined forensic short tandem repeats (STRs), lack of standardized and validated PCR protocols, STR reagent kits, and poorly developed nomenclature. A nomenclature system was established based on internationally recognized recommendations for human forensic STRs for a recently developed canine STR reagent kit. Representative alleles were sequenced from each of the 18 STRs and the sex-typing marker included in the kit. This study also reflects on the impact of point mutations, insertions, and deletions within and outside the STR core repeat structures. An understanding of the STRs' sequence and repeat structures will enable development of a robust and reliable allele nomenclature and improve the accuracy and precision of allele fragment sizing in canine forensic profiling. The expected allele sizes have been calculated, and their repeat stuctures defined based on sequence information.

Canine population data generated from a multiplex STR kit for use in forensic casework.

Canine biological specimens are often part of the physical evidence from crime scenes. Until now, there have been no validated canine-specific forensic reagent kits available. A multiplex genotyping system, comprising 18 short tandem repeats (STRs) and a sex-linked zinc finger locus for gender determination, was developed for generating population genetic data assessing the weight of canine forensic DNA profiles. Allele frequencies were estimated for 236 pedigreed and 431 mixed breed dogs residing in the U.S. Average random match probability is 1 in 2 x 10(33) using the regional database and 1 in 4 x 10(39) using the breed dataset. Each pedigreed population was genetically distinct and could be differentiated from the mixed breed dog population but genetic variation was not significantly correlated with geographic transition. Results herein support the use of the allele frequency data with the canine STR multiplex for conveying the significance of identity testing for forensic casework, parentage testing, and breed assignments.

Developmental validation of short tandem repeat reagent kit for forensic DNA profiling of canine biological material.

AIM: To develop a reagent kit that enables multiplex polymerase chain reaction (PCR) amplification of 18 short tandem repeats (STR) and the canine sex-determining Zinc Finger marker. METHODS: Validation studies to determine the robustness and reliability in forensic DNA typing of this multiplex assay included sensitivity testing, reproducibility studies, intra- and inter-locus color balance studies, annealing temperature and cycle number studies, peak height ratio determination, characterization of artifacts such as stutter percentages and dye blobs, mixture analyses, species-specificity, case type samples analyses and population studies. RESULTS: The kit robustly amplified domesticated dog samples and consistently generated full 19-locus profiles from as little as 125 pg of dog DNA. In addition, wolf DNA samples could be analyzed with the kit. CONCLUSION: The kit, which produces robust, reliable, and reproducible results, will be made available for the forensic research community after modifications based on this study's evaluation to comply with the quality standards expected for forensic casework.