Developmental validation study of a 24-plex Y-STR direct amplification system for forensic application

In the present study, validation data for 24 Y-STR loci from the Microreader™ 24Y Direct ID System was presented. Eight Y-STR loci have PCR product sizes with less than 220 bp in this multiplex amplification system, which can better detect degraded DNA samples from a crime scene. Developmental validation studies were conducted following the SWGDAM guidelines and consisted of PCR-based studies, sensitivity testing, species specificity, stability studies, accuracy and reproducibility evaluation, mixture studies, and case-type samples. The genetic diversities and forensic parameters of the 24 Y-STR loci were also investigated in Jiangsu Han population. Results demonstrated that this kit had the characteristics of high detection accuracy, strong species specificity, favorable anti-inhibition effect, and high sensitivity, and the minimum detection amount was 125 pg. When the mixed female template amount was below 3.2 times that of the male, or the male-male mixed ratio did not exceed 1:9, the typing results produced by 24Y Direct System still exhibited a higher discriminating ability for the mixture. The system was compatible with some typical biological samples such as bloodstain, hair, buccal swab, rib cartilage, and nail. The haplotype diversity (HD) and discrimination capacity (DC) of the 24 Y-STR loci were 0.9952 and 0.8500, respectively. The results revealed that the 24 Y-STR loci were highly polymorphic in Jiangsu Han population and could be useful for forensic cases and population genetic studies.