Ancestry prediction efficiency of the software GenoGeographer using a z-score method and the ancestry informative markers in the Precision ID Ancestry Panel.

We compared the efficiency of the freely available software GenoGeographer that includes a z-score based analysis with that of a naïve method based on the maximal likelihoods of 164 of the 165 ancestral informative markers (AIM) that are included in the commercially available kit Precision ID Ancestry Panel from Thermo Fisher Scientific. The AIM profiles were obtained by investigations with the Precision ID Ancestry Panel in our laboratory and from SNP data in the literature and publically available databases. We established eight well-defined AIM reference population data sets from 3603 AIM profiles. Six reference populations with profiles from multiple populations (Sub-Saharan Africa, North Africa, Middle East, Europe, South/Central Asia, East Asia), and two populations with individuals with admixed ancestry (Somalia and Greenland). By means of GenoGeographer and naïve calculations of the maximal likelihoods, 566 AIM profiles from individuals that were not included in the reference populations and expected to belong to one of the eight reference populations were tested. An initial standard z-score based test with GenoGeographer demonstrated that 22.4% of the individuals could not be assigned to any of the reference populations. Among the remaining 77.6% of the individuals, 83.6% were assigned to the reference population that was concordant with the specified populations of origin of the individuals, 8.2% had ambiguous assignments because they could belong to both the specified population of origin and one or more of the other populations, and 8.2% were assigned to a reference population that was discordant from the specified population of origin. A naïve assignment based on the maximal likelihood resulted in 78.1% concordant and 21.9% discordant assignments. The results demonstrate that the z-score analysis with GenoGeographer can reduce the error rate with a factor of almost three compared with that of the naïve estimation based on the maximal likelihoods of the AIM profiles. The Precision ID Ancestry Panel is a useful kit for the assignment of ancestry of the eight investigated populations that included two admixed populations. More AIMs with better discrimination and more data on the distribution of AIMs in relevant populations are needed to improve the efficiency of genogeographic prediction with AIMs on a worldwide basis.

Sequencing of 231 forensic genetic markers using the MiSeq FGx™ forensic genomics system - an evaluation of the assay and software.

The MiSeq FGx™ Forensic Genomics System types 231 genetic markers in one multiplex polymerase chain reaction (PCR) assay. The markers include core forensic short tandem repeats (STRs) as well as identity, ancestry and phenotype informative short nucleotide polymorphisms (SNPs). In this work, the MiSeq FGx™ Forensic Genomics System was evaluated by analysing reproducibility, sensitivity, mixture identification and forensic phenotyping capabilities of the assay. Furthermore, the genotype calling of the ForenSeq™ Universal Analysis Software was verified by analysing fastq.gz files from the MiSeq FGx™ platform using the softwares STRinNGS and GATK. Overall, the performance of the MiSeq FGx™ Forensic Genomics System was high. However, locus and allele drop-outs were relatively frequent at six loci (two STRs and four human identification SNPs) due to low read depth or skewed heterozygote balances, and the stutter ratios were larger than those observed with conventional STR genotyping methods. The risk of locus and allele drop-outs increased dramatically when the amount of DNA in the first PCR was lower than 250 pg. Two-person 50:1 mixtures were identified as mixtures, whereas 100:1 and 1 000:1 mixtures were not. Y-chromosomal short tandem repeats (Y-STRs) alleles were detected in the 100:1 and 1 000:1 female/male mixtures. The ForenSeq™ Universal Analysis Software provided the data analyst with useful alerts that simplified the analysis of the large number of markers. Many of the alerts were due to user-defined, locus-specific criteria. The results shown here indicated that the default settings should be altered for some loci. Also, recommended changes to the assay and software are discussed.

Evaluation of the Precision ID Ancestry Panel for crime case work: A SNP typing assay developed for typing of 165 ancestral informative markers.

The application of massive parallel sequencing (MPS) methodologies in forensic genetics is promising and it is gradually being implemented in forensic genetic case work. One of the major advantages of these technologies is that several traditional electrophoresis assays can be combined into one single MPS assay. This reduces both the amount of sample used and the time of the investigations. This study assessed the utility of the Precision ID Ancestry Panel (Thermo Fisher Scientific, Waltham, USA) in forensic genetics. This assay was developed for the Ion Torrent PGM™ System and genotypes 165 ancestry informative SNPs. The performance of the assay and the accompanying software solution for ancestry inference was assessed by typing 142 Danes and 98 Somalis. Locus balance, heterozygote balance, and noise levels were calculated and future analysis criteria for crime case work were estimated. Overall, the Precision ID Ancestry Panel performed well, and only minor changes to the recommended protocol were implemented. Three out of the 165 loci (rs459920, rs7251928, and rs7722456) had consistently poor performance, mainly due to misalignment of homopolymeric stretches. We suggest that these loci should be excluded from the analyses. The different statistical methods for reporting ancestry in forensic genetic case work are discussed.

Automated extraction of DNA from biological stains on fabric from crime cases. A comparison of a manual and three automated methods.

The presence of PCR inhibitors in extracted DNA may interfere with the subsequent quantification and short tandem repeat (STR) reactions used in forensic genetic DNA typing. DNA extraction from fabric for forensic genetic purposes may be challenging due to the occasional presence of PCR inhibitors that may be co-extracted with the DNA. Using 120 forensic trace evidence samples consisting of various types of fabric, we compared three automated DNA extraction methods based on magnetic beads (PrepFiler Express Forensic DNA Extraction Kit on an AutoMate Express, QIAsyphony DNA Investigator kit either with the sample pre-treatment recommended by Qiagen or an in-house optimized sample pre-treatment on a QIAsymphony SP) and one manual method (Chelex) with the aim of reducing the amount of PCR inhibitors in the DNA extracts and increasing the proportion of reportable STR-profiles. A total of 480 samples were processed. The highest DNA recovery was obtained with the PrepFiler Express kit on an AutoMate Express while the lowest DNA recovery was obtained using a QIAsymphony SP with the sample pre-treatment recommended by Qiagen. Extraction using a QIAsymphony SP with the sample pre-treatment recommended by Qiagen resulted in the lowest percentage of PCR inhibition (0%) while extraction using manual Chelex resulted in the highest percentage of PCR inhibition (51%). The largest number of reportable STR-profiles was obtained with DNA from samples extracted with the PrepFiler Express kit (75%) while the lowest number was obtained with DNA from samples extracted using a QIAsymphony SP with the sample pre-treatment recommended by Qiagen (41%).