A Simple Method of VNTR D1S80 Locus Allelic Ladder Construction for Capillary Electrophoresis-based Genotyping

Construction of an in-house allelic ladder for Canine Genotypes™ Panel 2.1 Kit

Dogs (Canis lupus familiaris) are among the most common companion animals in the Republic of Korea. Recently, there have been many criminal cases of dog cruelty, injury, and theft, among others. This has increased the importance of dog-related biological evidence at crime scenes. The National Forensic Service of the Republic of Korea conducts short tandem repeat (STR) analysis using the Thermo Scientific Canine Genotypes™ Panel 2.1 Kit (Canine Kit) to identify individual dogs through forensic analysis. The Canine Kit was developed as a forensic STR kit for the identification of individual dogs. However, an allelic ladder was neither developed nor included in the commercial kit, leaving an issue of accurate genotyping. Primer details for the 18 markers used in the Canine Kit are proprietary information, and thus, unavailable to end-users. In this study, an allelic ladder was constructed with 160 fragments by combining 158 fragments of STR alleles obtained by nested PCR and two fragments artificially obtained from the sex-determination marker. By including the new allelic ladder in analysis of samples amplified with the Canine Kit, the accuracy and reliability of data analysis were improved. Application of this allelic ladder would be helpful for interlaboratory data sharing and standardization of canine genotype databases.

Rapid oral bacteria detection based on real-time PCR for the forensic identification of saliva

This study developed a new method for forensic saliva identification using three oral bacteria, Streptococcus salivarius, Streptococcus sanguinis, and Neisseria subflava, combined with a real-time polymerase chain reaction (RT-PCR) system we called OB mRT-PCR. Analytical sensitivity results showed that the target bacteria were amplified at 102-107 copies/reaction, and analytical specificity was assessed using 24 other viruses, bacteria, and protozoa. To evaluate the OB mRT-PCR kit for forensic applications, saliva from 140 Korean individuals was tested, and at least two target bacteria were detected in all the samples. Additional studies on non-saliva samples demonstrated the specificity of the kit. Comparison of the kit with two conventional saliva test methods, the SALIgAE and RSID-Saliva assays, indicated that it was more sensitive and applicable to saliva samples in long-term storage (up to 14 weeks). Additionally, through amplification of mock forensic items and old DNA samples (isolated without lysis of the bacterial cells, regardless of their Gram-positivity), we found that the kit was applicable to not only saliva swabs, but also DNA samples. We suggest that this simple RT-PCR-based experimental method is feasible for rapid on-site analysis, and we expect this kit to be useful for saliva detection in old forensic DNA samples.