Forensic Science International: Genetics Supplement Series最新文献

Short tandem repeats (STRs) incur in length mutations that involve the loss or gain of repeats. STR mutation rates are usually estimated considering the rates of observed Mendelian incompatibilities in one generation familial configurations. When considering multistep mutations, for the autosomal and X-chromosomal modes of genetic transmission, underestimations are inevitable when using this approach (MIA), due to the occurrence of mutational events deceptively perceived as involving fewer steps. The rate of this occurrence depends on the mode of genetic transmission considered, the parental origin of the mutation, the type of familial configuration considered, and the genotypic background of the progenitor(s). MIA biases were weighted and compared for the diploid and haplodiploid modes of transmission, using familial genotypic configurations (parent(s)-child duos and trios) generated resorting to Python™ and real population databases from Norway, Somalia, and Spain for 10 Aut-STRs and Argentina, Eastern Asia, and Northern Europe for 12 X-STRs. One two- or one three-step mutation was simulated in each of the 1,000,000 familial configurations. The frequency with which mutations could be interpreted as involving fewer steps, when the most parsimonious reasoning is employed, was computed. Results showed that the magnitude and type of biases depend on the type of familial data and the genetic mode of transmission considered, being higher in duos than in trios, both in autosomes and the X chromosome. Indeed, whether X- or Aut-STRs are analyzed, trios generally provide better estimates and should be favored over duos. The pooling of the two types of data is not advised. The greater the number of steps involved in the mutation, the worst the estimates obtained. In X-chromosomal analyzes, trios with a paternal mutation presented the best estimates and mother-daughter duos the worst; mother-son duos showed similar estimates to trios when a maternal mutation was considered.

Sample disruption was a necessary step for DNA isolation. Bone and teeth were useful biological sources particular in human remains and advance decomposed bodies. The compact bone and teeth required several preparation steps prior to analyzing process. However, the methods in standard protocol were laborious and time consuming. An alternating pulverization, bead beating homogenizer, was purposed in its effectiveness for forensic casework. (1) Here, we applied this technique to the burnt cracked bone and tooth that recovered from house fire for forensic DNA analysis. After cleansed an external surface, the eight multidirectional motion tissue homogenizer, Precellys® evolution, was utilized to pulverize bone and tooth followed by a DNA extraction and amplification. For detection with a capillary electrophoresis, full profiles of autosomal STRs and Y-chromosomal STRs were recovered from tooth sample but the partial profile STR was demonstrated in bone sample. The new technique in bone homogenization was less time consuming (around 30 s), less exposure to chemical agents (no need of liquid nitrogen), high efficiency, with high-throughput productivity.

The evaluation of forensic DNA expert opinions (in some countries expert witness testimonies) and the way it affects criminal judgement is of paramount importance. We have selected one of the largest challenges when it comes to the evaluation of forensic DNA evidence, contamination of DNA samples, and examined how it influences the decisions judges make about the credibility of DNA evidence in Hungary.

In crime scenes, not all biological stains are human in origin. Some exhibits can be from pets living on the premises or from animal products used in food consumption. In addition, it could be necessary to test animal carcasses for other forensic purposes. Often such stains can include mixtures involving humans or other species. Thus, identifying and deconvoluting mixtures of species commonly found in and around a household can be crucial in forensic casework. Different molecular techniques have been employed for species identification such as immunoprecipitation, qPCR, and DNA sequencing.

In this project, a nanoplate-based digital PCR assay for species identification was developed, targeting Homo sapiens, canine, feline, bovine swine, pisces, and gallus in two multiplexes. An internal positive control was included in the design. The assay is simple, rapid, and can determine a wide variety of different vertebrates from biological exhibits, as well as in mixtures. Because the assay utilizes digital PCR, the procedure shows sensitivity down to a few copies, even in the presence of larger amounts of a major contributor, making the assay particularly useful in mixture deconvolution. Overall, this assay presents the forensic community with a novel application in which digital PCR can provide a sensitive and specific determination of species.

Determining the biological origin of body fluid evidence from crime scenes is extremely important for criminal investigation, especially in sexual assault cases. In Brazil, sexual crimes still present low-resolution rates, where approximately 8% of cases are judged. The determination of the presence of semen in samples from crime scenes as a test prior to DNA analysis is a mandatory requirement in forensic analysis and can help to better understand the dynamics of the event. This report aims to present the methodological strategy used in a criminal case of a home invasion where a t-shirt containing visible stains similar to human semen was found at the site. Convencional tests to detect the presence of PSA and sperm cells were performed on the fabric cutouts which showed negative results. We then processed the fabric samples for genetic analysis after two-years-storage, where were performed automated method for the genetic material isolation (QIAcube, Qiagen). The Real-time PCR analysis were carried out using the SOLIScript 1-step SolisGreen (SolisBiodyne) kit, with specific primers to the TGM4 (Transglutaminase 4) gene, in the Rotor Gene Q-5Plex HRM equipment (Qiagen). The results obtained for the melt curve indicated the presence of human semen in the analyzed samples. After the HRM-qPCR assay we also analyzed the a-STR and Y-STR markers. All the results were useful for the criminal process, which led to the identification of the author of the crime.

Microbial communities in biological stains can provide valuable information to assist forensic scientists identify the body fluid/tissue present in these. As these microbial communities are characteristic of body habitats, DNA sequencing of microbes can be used to predict bodily origin. Promising predictive results have been obtained with supervised machine learning algorithms trained on bacterial abundance data from human body sites. Importantly, prediction accuracy is dependent on the training dataset, yet compiling a large and comprehensive training reference is a non-trivial issue requiring substantial efforts. Here we present a new online database and associated data-mining platform which is, to our knowledge, the first one customised for forensic scientists investigating body fluids/tissues. Our database features samples originating from ten human body sites, with selection options through an online platform. Users can download bacterial abundance as well as taxonomic data, which can then be used to train predictive models and test their accuracy. Future stages of the development of the platform will include curation of the samples to decrease potential errors in sample labelling, as well as access to an online tool to conduct exploratory analyses.

Our previous work focused on validation the SureID 23comp Human Identification Kit (Health Gene Technologies, China), 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 from the population of Saudi Arabia. The kit genotypes 22 STRs, 17 of which are non-CODIS, and Amelogenin. The validation tests showed that it has the potential to increase the power of testing in complex cases.

In this paper, the allele frequency data, common forensic parameters for the 17 non-CODIS STR loci are presented. We found the majority of loci had an excess of homozygosity in the data set, which is most likely explained by the relatively high levels of consanguinity in the population of Saudi Arabia.

In the present study the genetic variation of different Peruvian populations was investigated. The samples for this study were obtained from 669 individuals distributed among 11 populations from Peru. All samples were analyzed using 23 autosomal STR markers. The Arlequin v3.5.2.2 software was used to determine the genetic distances (Fst) of the studied populations. Notable population substructure was detected between some populations.

The continuous admixture events among Europeans, Native Americans, and Africans occurred differently throughout the Ecuadorian territory, creating a diversified genetic composition. Therefore, to evaluate how the genetic diversity is partitioned along the country for 15 STRs, 842 admixed-population samples were analyzed. We also evaluated the effect of applying an adjustment for population structure when estimating LRs using a national database. The results showed that to accurately assess forensic evidence, the use of a national database may be justified with the application of an appropriate adjustment for population structure.

We analyzed the accumulation of population polymorphism in 2504 individuals - nuclear genomes (nDNA) of 26 populations (81 genes associated to extreme environments) and 3295 mitochondrial genomes (mtDNA) of 47 populations with the aim to found mitonuclear relationship associated an extremes environment as altitude. For that, we use an algorithm developed by us to determine the accumulation of polymorphisms by segments in the genome and thus be able to perform the multivariate analysis to found SNPs differences and similarities among populations. The results showed in Peruvian population a statistically significant mitonuclear relationship for 113/293970 nDNA SNPs in 16/81 genes. In the case of the mtDNA, we found a statistically significant mitonuclear relationship for 6/22 mtDNA positions – Gene. Additionally for the Peruvian population, the MRPP3 had the greatest polymorphism contribution with respect to other populations. Then, these nDNA and mtDNA SNPs in genetically close populations to Peru can be applied to forensic genomic phenotyping to identify groups likely adapted to extreme conditions (such as altitude) or make individualization between low and high altitude populations.