Forensic Science International: Genetics Supplement Series最新文献

This study aimed to investigate genetic diversity and ancestry in Afro-descendants from the Andes (AN) and the Pacific Coast (PC) regions of Ecuador, using autosomal and lineage markers. CR-mtDNA and PPY23-STRs showed high haplotype diversities. Statistically significant differences were found between AN and PC. Due to different patterns of sex-biased matting, differences between regions were more pronounced for the mtDNA than for the Y-chromosomal markers. A lower African ancestry was detected in AN than PC, for autosomal and both maternal and paternal lineage markers.

Capillary electrophoresis (CE) analysis of short tandem repeats (STRs) and single nucleotide polymorphisms (SNPs) use a stochastic threshold to consider the possibility of missing alleles (dropouts) or detecting additional alleles (drop-ins). In CE, this threshold may be approximately 200 RFU, and peak heights are assessed relative to this threshold. In next generation sequencing (NGS), also known as massively parallel sequencing (MPS), STRs are identified by their sequence, and specific alleles are identified by their repeat number and intra-allelic variation. Abundance is approximated by the number of sequence reads for each allele. The total number of reads generated for each marker in a sample depends on factors such as the numbers of samples pooled for sequencing, the number of markers in the assay, the integrity and quantity of the input DNA sample, and the inter-locus balance of the assay. For multiplexes that contain both autosomal and sex-linked markers, the biological sex of the sample also influences total reads per locus. To normalize these variables and better establish a robust stochastic threshold, a sample-wide metric is proposed for estimating the possibility of dropouts or drop-ins based on the variance of the inter-locus balance of the markers across a sample. The intuition is that samples with variable allele balance globally are more likely to have noisier data and therefore require more stringent read count thresholds. This method is robust to sequencing multiplexity, biological sex and manufacturing lot variation.

The interest in the analysis of the human microbiome for personal identification purposes is based on the microbial diversity amongst individuals. The oral cavity hosts one of the most diverse and abundant microbial communities in the human body; the skin instead is a complex living ecosystem with unique microbial niches at different sites. Both skin and oral microbiomes are highly individual and relatively stable over time. As saliva and skin debris are often found at crime scenes, the analysis of their microbiome may represent a potential tool for personal identification. However, there are some gaps in knowledge on how factors such as age, sex, geographic origin, diet and pathologies can affect the composition of the microbiome. The aim of this study is to improve the existing knowledge by examining oral and skin microbiomes from the same individuals and evaluating the variability between anatomical sites and donors. For this study, 50 individuals living in Italy donated oral swab samples and provided information regarding their diet, lifestyle, health status, antibiotic use, and other demographic data. Skin swabs from 11 of the 50 individuals were also analysed and compared to the oral swabs from the same donors. All analyses were done through metabarcoding of the 16S rRNA region of DNA extracted from the samples. This research outlines the potential use of oral and skin microbiome signatures as added evidence in personal identification, providing useful investigative clues for future forensic caseworks.

Analysis of genetic profiles obtained from low template DNA samples (LT DNA) can be challenging because of increased probability of stochastic amplification artifacts occurrence. According to the recommendations of international genetic societies the quality of the LT-DNA traces results can be improved by applying low copy number (LCN) methods. Another strategy which allows to obtain better results of the analysis of LT-DNA traces is replicate the amplification of the same DNA sample and create consensus, composite (virtual pool profile) or real pool profile. The aim of the research was to analyze and compare the efficiency of modifications used in the testing of LT-DNA samples. Obtained results indicate that implementation of these methods in laboratory practice may lead to improvement in the quality of reported data from LT-DNA traces in genetic analyzes conducted to assist the justice system.

After developing an LR-system to calculate weight of evidence from mRNA data [1] we here present how this LR-system is used in forensic casework. We aim to convey the weight of the evidence in forensic reports.

Forensic DNA analysis has the potential to provide useful information for criminal justice even in cases where there is no match, neither between the DNA profile generated from the crime scene and the existing DNA profiles in criminal databases, nor between the DNA collected at a crime scene and potential suspects. In contrast to traditional forensic genetic testing, forensic familial DNA searching does not provide evidence, but helps to generate investigative leads and narrow down the range of potential offenders. The aim of this study is to examine, whether there is a need for special regulation of this topic in Hungary.

At the Netherlands Forensic Institute, mRNA profiling for the purpose of organ tissue identification is frequently requested in casework. The previous version of the assay (denoted Organtyper) lacked markers for identifying adipose tissue, while this was occasionally questioned in casework. Here, three potential adipose markers are examined before incorporating one into the final Organtyper assay. The added value of the adipose marker becomes clear from looking at casework results.

Microhaplotypes are markers that consist of haplotype blocks of SNPs, which can be analyzed by massively parallel sequencing technologies. These allow determining the haplotype phase at every locus by clonal sequencing each DNA strand. MHs are polymorphic loci with same size alleles, no stutter, and lower mutation rate than STRs. They can provide the same power of discrimination of STR-kits, thus useful for mixture deconvolution, but more accurate ancestry prediction than STRs. In this study we investigated the potential of a recently developed 74plex-MH panel for kinship testing using the Familias software.

Samples from families of four major US population groups were collected and genotyped using the 74plex-MH panel. MH allele frequency data from 347 individuals were imported into Familias software along with STR allele frequency data of 29 loci (NIST dataset) from 1036 individuals. Different family scenarios were tested and these included unrelated vs parent-child, unrelated vs full siblings, unrelated vs half siblings, unrelated vs cousin pairs. The prediction of the kinship relation for the four populations of interest was reported as Log10 of the likelihood ratio (LR).

Overall, the panel of 74MHs and 29STRs showed similar performance in predicting the correct kinship scenarios tested. Correct prediction was reported for parent-child, full siblings, and half sibling scenarios, but not for the cousin pairs scenario. The panel of 74 MHs showed larger Log10LR values than the 29 STR-assay, thus demonstrating the effectiveness of this biomarker as a tool for kinship testing in addition to mixture deconvolution and ancestry prediction.

The transfer, persistence, prevalence, and recovery of DNA (DNA-TPPR) can be highly relevant in forensic investigations to evaluate the presence and/or actions of a person of interest (POI). Whilst the DNA-TPPR-related research has increased significantly over the last decade, there is a lack of data on companion animals and their relationship to human DNA transfer. Given the commonality of cats and dogs in households around the world, companion animals as receptors and vectors for DNA transfer can be highly relevant in cases involving animals as victims of a criminal offense, or cases requiring activity level evaluations. Samples were collected from an external area on the right side of 20 cats to determine the prevalence and sources of human DNA on this area. Preliminary data shows that human DNA is present on household cats, its source is mainly from household inhabitants. Further studies are required to elucidate the means and level of transfer of human DNA to and from cats and other household animals. This knowledge can be relevant to sample targeting in specific case circumstances and/or when considering possible means of the presence of a person’s DNA at the crime scene location.

Human eye colour variation is strongly associated with single nucleotide polymorphisms (SNPs) in the OCA2-HERC2 locus, especially rs12913832 that is found in an enhancer element of OCA2. In a previous study we found that 43 out of 166 individuals in a Norwegian population with the brown eye colour genotype HERC2 rs12913832:AA or AG, did not have the expected brown eye colour. To investigate if duplications or deletions in the OCA2-HERC2 locus could explain the blue eye colour in these individuals, we analysed massively parallel sequencing (MPS) data for copy number variations (CNVs) in the OCA2-HERC2 region. The ∼500 kb long OCA2-HERC2 locus was sequenced in 94 individuals with the rs12913832:AG and AA genotypes. Of these, 43 were observed to have blue eye colour and 51 were observed to have brown eye colour. CNVs were analysed using R and the R-package panelcn.MOPS - CNV detection tool for targeted NGS panel data. In rs12913832:AG individuals, CNVs in 32 regions were significantly associated with blue eye colour (Benjamini-Hochberg adjusted p-value ≤ 0.05). In rs12913832:AA individuals, CNVs in 14 regions were associated with blue eye colour using raw p-values (p ≤ 0.05). The functional effects of these CNVs on OCA2 expression are yet to be investigated. However, this study suggests that CNVs in the OCA2-HERC2 locus might explain why some of the rs12913832:AG and AA individuals have unexpectedly blue eyes.