Analysis of linkage and linkage disequilibrium for syntenic STRs on 12 chromosomes

Development and validation of novel 8-dye short tandem repeat multiplex system for forensic applications

DNA profiling of short tandem repeats (STRs) is the primary method for genotyping forensic samples. However, degraded DNA and trace samples are still major problems for commercial 5- or 6-dye STR kits. In order to improve the performance of this method, we developed a novel 8-dye STR multiplex system containing 18 autosomal loci (D3S1358, D1S1656, TPOX, D16S539, vWA, D6S1043, D2S1338, CSF1PO, D19S433, D7S820, FGA, D8S1179, D5S818, D13S317, TH01, D21S11, D12S391, and PentaD) and the sex-determining locus Amelogenin, with all fragments smaller than 330 bases. Validation was carried out as recommended by the Scientific Working Group on DNA Analysis Methods. The results showed that complete profiles were obtainable when the input DNA was as low as 0.0625 ng. Full profiles were obtained even in the presence of inhibitors such as humic acid (< 300 ng/μl), hematin (< 100 μM), and indigo (0.01%). The 8-dye STR multiplex system also showed good performance in the detection degraded DNA samples. These results indicate that the 8-dye STR multiplex system is suitable for human DNA genotyping, including for difficult forensic materials.

An evaluation of the SureID 23comp Human Identification Kit for kinship testing

Short tandem repeat (STR) profiling has been routinely used in kinship testing since the introduction of commercial kits in the mid-1990s. While 15 to 23 STR loci normally give definitive results in simple kinship testing, additional loci are sometimes required to resolve complex cases. The SureID 23comp Human Identification Kit, recently released by Health Gene Technologies (China), multiplexes amelogenin and 22 autosomal STRs, 17 of which are non-CODIS STRs. This enables the profiling of 38–40 loci when used in conjunction with widely used commercial kits. In this study, the kit was evaluated for kinship applications as a supplementary STR kit following the minimum criteria for validation recommended by the European Network of Forensic Science Institutes (ENFSI) and the Scientific Working Group on DNA Analysis Methods (SWGDAM) using 500 samples. Performance was comparable with other commercial kits demonstrating: repeatability and reproducibility; precision (maximum s.d. 0.1048 nt); accuracy, all alleles were within ±0.41 nt compared to the actual sizes; heterozygous peak balances at all loci >68%; stutter ratios ranged from 3.8% to 16.15%; full profiles were generated with 125 pg DNA (95.12% of alleles at 62 pg),; and we found 100% concordance over 5 common STRs with the GlobalFiler kit.

Evaluation of the InnoTyper® 21 genotyping kit in multi-ethnic populations

We report the findings of the evaluation of the InnoTyper^® 21 genotyping kit for the use of human identification (HID) and paternity testing in South Africa. This novel forensic kit evaluates 20 retrotransposable elements (AC4027, MLS26, ALU79712, NBC216, NBC106, RG148, NBC13, AC2265, MLS09, AC1141, TARBP, AC2305, HS4.69, NBC51, ACA1766, NBC120, NBC10, NBC102, SB19.12 and NBC148) and the Amelogenin locus for sex determination. The evaluation of the genotyping performance showed no significant spectral pull-up for peak heights between 100 and 30,000 RFUs. All loci presented biallelic patterns except the triallelic RG148 locus resulting from a variant insertion allele, named RG148I-1, observed exclusively in the Bantu. The InnoTyper^® 21 kit was found to be highly discriminatory between the 507 unrelated individuals of the Afrikaaner, Asian Indian, Coloured, amaXhosa and amaZulu groups. The HID parameters: the CPD ranged between 0.99999987 and 0.9999999845, and the CMP between 1.0335×10^-7 and 1.5506×10^-8. The paternity parameters: the CPI ranged between 0.0202 and 0.3177, and the CPE between 0.9161 and 0.9749. There were no significant signs of deviations from HWE or linkage disequilibrium (LD) after applying a Bonferroni correction. This kit also showed minor levels of population structure which could differentiate between the African and non-African population groups. Finally, in challenging casework with severely degraded biological material, the InnoTyper^® 21 genotyping kit was compatible with GlobalFiler^® and Investigator DIPplex^® to increase the HID parameters.