Developmental validation of a novel 8-dye fluorescent typing system with 59 Y-STRs and 3 Y-indels for forensic...

An 8-dye fluorescence-labeling forensic Y-chromosomal short tandem repeats (Y-STRs) kit, the 62-plex Y-STR multiplex amplification system, was developed and optimized. The system was validated by testing PCR conditions, stutter ratios (SR) and peak height ratios, sensitivity, mixture samples, precision and accuracy, species-specificity, and inhibition studies according to the Scientific Working Group on DNA Analysis Methods guidelines. PCR-based studies showed that the recommended PCR conditions were optimized for this kit. In the sensitivity study, a full profile was obtained from template DNA with a quantity of u125 pg. Consistent profiles were obtained from three different laboratories. The SRs in all loci were less than 15%, and nice balance and suitable average peak height were shown. No peaks were detected in the profiles of common animal species and microorganisms. In the male-male mixture studies, all loci were observed at a ratio of 1:8, and in the male-female mixture study, all alleles could be profiled at a ratio of 1:500 if the male DNA inputs were ≥0.5 ng/µL. An inhibitor study demonstrated that the kit had varying degrees of resistance to the presence of common inhibitors. Population study demonstrated the 62-plex Y-STR Kit improved the power of discrimination in unrelated Chinese Han males (n = 192). When haplotype diversity was 1, the probability of discrimination power of the 62-plex Y-STR Kit was 0.9948, which is suitable for forensic investigations. The results show that the developed 8-dye fluorescence labeling 62 loci system is sensitive, robust, convenient, and highly informative for forensic applications.