Forensic Genetics as a Tool for Peace and Justice: An Overview on DNA Quantification

In Forensic Genetics, DNA analysis is performed to obtain a Short Tandem Repeat (STR) profile from an evidence sample, which is then compared with the victim and suspect(s) reference sample STR profile, to determine their contribution to that evidence sample. However, forensic biological samples can be present in low quantities and be exposed to different environmental insults leading to DNA degradation and contamination by inhibitor compounds. Thus, it is desirable for a forensic scientist to have useful information about the forensic sample quantity and quality prior to STR amplification. New methods in Forensic DNA analysis for detecting, preserving, and quantifying DNA, as well as its recovery from different biological materials are continually being developed. Real-Time PCR (RT-PCR) assays for DNA quantification, like the recent Quantifiler® Duo DNA quantification kit (Applied Biosystems) proved to be very useful in forensic samples. Since many samples, mainly those resulting from sexual assault cases are often composed by unbalanced male/female DNA mixtures, the knew RT-PCR quantification assay, developed to quantify relative male/ female DNA ratio contributes not only to total DNA determination but also to ascertain the presence and quantity of enough male DNA in the sample. These results are important to guide the optimal STR analysis selection, such as autosomal STR, Y-STR, or mini-STR, increasing downstream analysis success rates. In this work we present real forensic casework where the DNA amount and quality were important to guide the selection of the appropriate STR amplification kit in order to increase the success of profiling in the first attempt, reducing the number of samples that need to be reprocessed and thereby decreasing the turn around time in a forensic laboratory.info:eu-repo/semantics/publishedVersio

Population Genetic Data for F13A01, FES/FPS, F13B and LPL in the South Portuguese Population

Poster apresentado no 24th World Congress of the International Society for Forensic Genetics, Viena (Austria), 2011DNA parentage testing is currently performed using several highly polymorphic short tandem repeats (STRs). In our routine casework, we apply two validated STRs kits, in order to have results in the 13 codis loci plus D2S1338, D19S433, PENTA E, PENTA D, and Amelogenin. In complex and deficient paternity cases it is often necessary to increment the number of studied STRs. For this reason, we introduced in our laboratory GenePrint® FFFL Multiplex kit, which can provide results in F13A1, FES/FPS, F13B, and LPL using the GenePrint® FFFL System (Promega, USA) kit. In this study, we analyzed 150 unrelated and healthy individuals from the south Portugal population. Allele frequencies and statistical parameters were estimated with Arlequin 3.5.1.2. Paternity Statistics were calculated using software package PowerStats v12. The forensic efficiency values suggested that loci F13A01, FES/FPS, F13B, and LPL are discriminative and very useful to solve complex forensic casework, and should be added to the set of STRs loci routinely used in Forensic laboratories. In conclusion, an additional 4 loci dataset was established for the south Portuguese population, which can be used for both forensic casework and complex kinship testinginfo:eu-repo/semantics/publishedVersio

Genetic portrait of Lisboa immigrant population from Cabo Verde with mitochondrial DNA analysis

"The aims of this study were (i) to enrich mtDNA global database, (ii) obtainment of the mtDNA variability of the Cabo Verde population living in Lisboa to complement previous studies by our group using STR genetic markers (Amorim et al. 2012; Afonso Costa et al. 2014), (iii) assign haplotypes to designated haplogroups, (iv) infer whether there are genetic proximity between the studied population and previous studies according to the mtDNA profile of the Cabo Verde population, and (v) compare the studied population with other African populations, with the aim to bring more light to our understanding on the subject of the impact of migrations involving Cabo Verde archipelago’s origin."info:eu-repo/semantics/publishedVersio

Sequencing CYP2D6 for the detection of poor-metabolizers in post-mortem blood samples with tramadol

Tramadol concentrations and analgesic effect are dependent on the CYP2D6 enzymatic activity. It is well known that some genetic polymorphisms are responsible for the variability in the expression of this enzyme and in the individual drug response. The detection of allelic variants described as non-functional can be useful to explain some circumstances of death in the study of post-mortem cases with tramadol. A Sanger sequencing methodology was developed for the detection of genetic variants that cause absent or reduced CYP2D6 activity, such as *3, *4, *6, *8, *10 and *12 alleles. This methodology, as well as the GC/MS method for the detection and quantification of tramadol and its main metabolites in blood samples was fully validated in accordance with international guidelines. Both methodologies were successfully applied to 100 post-mortem blood samples and the relation between toxicological and genetic results evaluated. Tramadol metabolism, expressed as its metabolites concentration ratio (N-desmethyltramadol/O-desmethyltramadol), has been shown to be correlated with the poor-metabolizer phenotype based on genetic characterization. It was also demonstrated the importance of enzyme inhibitors identification in toxicological analysis. According to our knowledge, this is the first study where a CYP2D6 sequencing methodology is validated and applied to post-mortem samples, in Portugal. The developed methodology allows the data collection of post-mortem cases, which is of primordial importance to enhance the application of these genetic tools to forensic toxicology and pathology.info:eu-repo/semantics/publishedVersio

Y-Filer Plus® genetic characterization of caucasian individuals from South Portugal

Trabalho apresentado sob a forma de poster na reunião cientifica - "Haploid Markers 2016 Update on DNA variation" Maio 20-21, Berlin, GermanyDue to their paternal inheritance, Y-STRs offers particular perspectives for identification and kinship analysis and are also a precious tool in sexual assault cases with relatively high amount of female DNA and also in mixtures from multiple male donors. Nonetheless their value, there are some limitations to their use in forensic investigations since their ability to discriminate between individuals is considerably lower than that of the autosomal STRs set, mainly in cases with close or distant patrilineal relatives.One of the most recently developed Y-STR kit, Y-Filer Plus® (Life Technologies, Foster city, USA), allows forensic geneticists to study 27 Y-chromosomal loci. All the 16 markers included in the Y-Filer® kit (Life Technologies, Foster city, USA), plus 9 additional markers: DYS576, DYS627, DYS460, DYS518, DYS570, DYS449, DYS481, DYF387S1 and DYS533, six of which (DYS576, DYS627, DYS518, DYS570, DYS449 and DYF387S1) are characterized as “rapidly mutating”, and can differentiate between unrelated individuals and possibly between male relatives.Allelic frequencies were estimated with Arlequin v. 3.5. Gene and Haplotype diversities were estimated according to Nei formula. The discrimination capacity was also calculated by dividing the number of different haplotypes by the total number of individuals in the sample. The fraction of unique haplotypes was determined as the percent proportion of unique haplotypes. In conclusion, the recently introduced Y-Filer Plus® system provides innovative discriminatory power for forensic applicationN/

Insertion/Delection Polymorphism and forensic aplications: A preliminary study

Poster apresentado na reunião científica "DNA in Forensics" em Innsbruck, Austria (2012)The human genetic identification is usually based on the study of STR markers, robust and reliable for samples containing relatively small quantities of DNA. Recent advances in forensic genetics have focused on the development of genotyping assays using shorter amplicons, in order to improve the successful amplification of degraded samples. Single Nucleotide Polymorphisms (SNP) and Insertion/Deletion polymorphisms (INDEL), length polymorphisms created by insertions or deletions of one or more nucleotides in the genome, have considerable potential in this kind of forensic samples, usually present in identification casework, since they can combine desirable characteristics of both, STR and SNP. In this study, a set of 30 biallelic Deletion/Insertion polymorphisms (DIP or INDEL) distributed over 19 autosomes plus Amelogenin in a single multiplex PCR reaction was applied to 100 healthy and unrelated caucasian individuals. Statistical analysis revealed that the 30 biallelic markers can provide satisfactory levels of informativeness for forensic demands.N/

The role of DNA concentrations in forensic casework results : regression models application

Póster apresentado no 28th Congress of International Society For Forensic Genetics (ISFG 2019), Praga, República Checa, 9-13 de Setembro de 2019In forensic DNA typing, short tandem repeats (STRs) are the most frequently genotyped markers in order to distinguish between individuals and to relate them to a crime or to exonerate the innocent. In recent years, new controversies have arisen with the advent of more sensitive techniques, allowing profiles to be recovered from minimum amounts of DNA, hence, bringing challenges to weight of evidence evaluation for forensic DNA profiles obtained from low template DNA samples. Introduction of interpretation models, or even new weight of evidence software should be accompanied by a measure of uncertainty that is part of any biological analysis. Specially, due to stochastic effects, the reliability of the obtained profiles might differ between machinery, workflow and also PCR settings in use in different laboratories. In this work we try to understand the relation between Peak Area, DNA concentration and also size marker, using adequate regression models. Buccal swabs from 180 individuals, with unknown identity, were selected for this study. DNA was extracted with prep-n-go™ buffer and quantified using Quantifiler® Trio DNA Quantification kit in a 7500 Real-Time PCR System (Applied Biosystems). STR amplification was performed with Powerplex Fusion 6C amplification kit (Promega). Amplified PCR products were separated and detected in an Applied Biosystems® 3500 Genetic Analyzer using manufacturer’s conditions. Electrophoresis results were analysed with GeneMapper® ID-X v1.4. Statistical analysis was performed with R Studio. Our results allow having an important overview about the relation between DNA concentrations, peak area, and size of the studied genetic markers.N/

Forensic genetic analysis of South Portuguese population with the six dye Powerplex® Fusion 6C

Poster apresentado no 28th Congress of International Society For Forensic Genetics (ISFG 2019), Praga, República Checa, 9-13 de Setembro de 2019As an improvement in efficiency and in Human Discrimination Power, the new six dye multiplex kit PowerPlex® Fusion 6C System, by Promega, available for human identification can co-amplify 27 loci, in a single reaction, have been introduced in the last years with great success. This kit allows the amplification and detection of autosomal loci included in the expanded Combined DNA Index System CODIS, plus the loci Penta D, PENTA E and SE33 as well as Amelogenin for gender determination. Furthermore, this kit includes three Y –STRs (DYS391, DYS576 and DYS570), allowing allelic attribution in a total of 27 loci. This genetic markers extension satisfies not only CODIS but also European Standard Set recommendations. Thinking about continuous human migration movements, especially in a very cosmopolitan region like Lisbon and south of Portugal, and also, in keeping population studies and actualized STR databases we decided to update our previous studies. Our sample is composed of 600 unrelated individuals, from paternity testing with laboratory identity anonymised. DNA was extracted by Prep-n-go BufferTM(Thermo-Fisher Scientific). PCR amplification was performed with PowerPlex® Fusion 6C System, according to manufacturer’s guidelines. Fragment analysis was carried out in an Applied Biosystems® 3500 Genetic Analyser. Electrophoresis results were analysed with GeneMapper® ID-X v1.4. Allele frequencies and population statistics, including Hardy-Weinberg equilibrium p-values from exact test probabilities and forensic parameters were calculated with adequate software. In conclusion, our population information was updated in order to apply most recent data in our casework weight of evidence.N/

Mitochondrial DNA data of Cabo Verde Immigrant Population Living in Lisboa

Póster apresentado em 8 th International Y Chromosome User Workshop 5 th International EMPOP Meeting, Innsbruck, September 06-08, 2012Mitochondrial DNA (mtDNA) analysis found an important role in forensic genetics, especially when nuclear DNA analysis does not give a conclusive response. It is a powerful tool to exclude samples as originating from the same matriline. Features that increase the vested interest of mtDNA are the high copy number per cell, maternal inheritance, absence of recombination, and high mutation rate. Due to the higher overall mutation rate, the control region is comparatively enriched in sequence variation and therefore its analysis is important to establish haplotypes and haplogroups. Haplogroup assignment became noteworthy to clarify the history and demographic past of a population. As well as occurring all over Europe, in Portugal, and particularly in Lisboa, immigrant populations are increasing. The Instituto Nacional de Medicina Legal e Ciências Forenses is carrying out a comprehensive genetic study with the aim of portraying the genetic diversity of the immigrants who live in Lisboa. Within that objective, the present study intends to: obtain the mtDNA variability of Cabo Verde Immigrant Population Living in Lisboa and classify haplotypes into haplogroups. The studied population shows great interpopulation genetic variability due to the high frequency of unique haplotypes. Cabo Verde immigrants living in Lisboa exhibit haplotypes that belong to haplogroups observed in native Africans and in West Eurasian. MtDNA control region typing is extremely useful as a technique to differentiate among degraded samples frequently found in forensic genetics and to establish its global frequency when having knowledge of the genetic structure of populations.N/