Forensic DNA Typing Research Articles

Developmental validation of QIAGEN Investigator® 24plex QS Kit and Investigator® 24plex GO! Kit: Two 6-dye multiplex assays for the extended CODIS core loci

The original CODIS database based on 13 core STR loci has been overwhelmingly successful for matching suspects with evidence. In order to increase the power of discrimination, reduce the possibility of adventitious matches, and expand global data sharing, the CODIS Core Loci Working Group determined the expansion of the CODIS core loci to 20 STR plus three additional “highly recommended” loci (SE33, DY391, Amelogenin) Hares, 2015, 2012 [1,2].The QIAGEN Investigator 24plex QS and Investigator 24plex GO! Kits are 6-dye multiplex assays that contain all markers of the expanded 23 CODIS core loci along with a unique internal performance control that is co-amplified with the STR markers. The “Quality Sensor“ generates additional information for quality control and performance checks. Investigator 24plex QS is designed for purified DNA from casework and reference samples, whereas 24plex GO! is dedicated to direct amplification of reference samples, like blood or buccal cells on FTA or swabs.A developmental validation study was performed on both assays. Here, we report the results of this study which followed the recommendations of the European Network of Forensic Science Institutes (ENFSI) [3] and the Revised Validation Guidelines of the Scientific Working Group on DNA Analysis Methods (SWGDAM) [4]. Data included are for PCR-based procedures e.g. reaction conditions, effects of PCR annealing temperature variations, amplification cycles or cyclers, sensitivity (also in the context of the Quality Sensor), performance with simulated inhibition, stability and efficiency, precision, reproducibility, mixture study, concordance, stutter, species specificity, and case-type samples. The validation results demonstrate that the Investigator 24plex QS and Investigator 24plex GO! Kits are robust and reliable identification assays as required for forensic DNA typing in forensic casework analysis and databasing.

Developmental validation of the DNAscan™ Rapid DNA Analysis™ instrument and expert system for reference sample processing

Since the implementation of forensic DNA typing in labs more than 20 years ago, the analysis procedures and data interpretation have always been conducted in a laboratory by highly trained and qualified scientific personnel. Rapid DNA technology has the potential to expand testing capabilities within forensic laboratories and to allow forensic STR analysis to be performed outside the physical boundaries of the traditional laboratory.The developmental validation of the DNAscan/ANDE Rapid DNA Analysis System was completed using a BioChipSet™ Cassette consumable designed for high DNA content samples, such as single source buccal swabs. A total of eight laboratories participated in the testing which totaled over 2300 swabs, and included nearly 1400 unique individuals. The goal of this extensive study was to obtain, document, analyze, and assess DNAscan and its internal Expert System to reliably genotype reference samples in a manner compliant with the FBI's Quality Assurance Standards (QAS) and the NDIS Operational Procedures.The DNAscan System provided high quality, concordant results for reference buccal swabs, including automated data analysis with an integrated Expert System. Seven external laboratories and NetBio, the developer of the technology, participated in the validation testing demonstrating the reproducibility and reliability of the system and its successful use in a variety of settings by numerous operators. The DNAscan System demonstrated limited cross reactivity with other species, was resilient in the presence of numerous inhibitors, and provided reproducible results for both buccal and purified DNA samples with sensitivity at a level appropriate for buccal swabs. The precision and resolution of the system met industry standards for detection of micro-variants and displayed single base resolution. PCR-based studies provided confidence that the system was robust and that the amplification reaction had been optimized to provide high quality results.The DNAscan integrated Expert System was examined as part of the Developmental Validation and successfully interpreted the over 2000 samples tested with over 99.998% concordant alleles. The system appropriately flagged samples for human review and failed both mixed samples and samples with insufficient genetic information. These results demonstrated the integrated Expert System makes correct allele calls without human intervention.

Genetic analysis of the Yavapai Native Americans from West-Central Arizona using the Illumina MiSeq FGx™ forensic genomics system

Forensically-relevant genetic markers were typed for sixty-two Yavapai Native Americans using the ForenSeq™ DNA Signature Prep Kit.These data are invaluable to the human identity community due to the greater genetic differentiation among Native American tribes than among other subdivisions within major populations of the United States. Autosomal, X-chromosomal, and Y-chromosomal short tandem repeat (STR) and identity-informative (iSNPs), ancestry-informative (aSNPs), and phenotype-informative (pSNPs) single nucleotide polymorphism (SNP) allele frequencies are reported. Sequence-based allelic variants were observed in 13 autosomal, 3 X, and 3 Y STRs. These observations increased observed and expected heterozygosities for autosomal STRs by 0.081±0.068 and 0.073±0.063, respectively, and decreased single-locus random match probabilities by 0.051±0.043 for 13 autosomal STRs. The autosomal random match probabilities (RMPs) were 2.37×10–26 and 2.81×10–29 for length-based and sequence-based alleles, respectively. There were 22 and 25 unique Y-STR haplotypes among 26 males, generating haplotype diversities of 0.95 and 0.96, for length-based and sequencebased alleles, respectively. Of the 26 haplotypes generated, 17 were assigned to haplogroup Q, three to haplogroup R1b, two each to haplogroups E1b1b and L, and one each to haplogroups R1a and I1. Male and female sequence-based X-STR random match probabilities were 3.28×10–7 and 1.22×10–6, respectively. The average observed and expected heterozygosities for 94 iSNPs were 0.39±0.12 and 0.39±0.13, respectively, and the combined iSNP RMP was 1.08×10–32. The combined STR and iSNP RMPs were 2.55×10–58 and 3.02×10–61 for length-based and sequence-based STR alleles, respectively. Ancestry and phenotypic SNP information, performed using the ForenSeq™ Universal Analysis Software, predicted black hair, brown eyes, and some probability of East Asian ancestry for all but one sample that clustered between European and Admixed American ancestry on a principal components analysis. These data serve as the first population assessment using the ForenSeq™ panel and highlight the value of employing sequence-based alleles for forensic DNA typing to increase heterozygosity, which is beneficial for identity testing in populations with reduced genetic diversity.

Effects of the Ion PGM™ Hi-Q™ sequencing chemistry on sequence data quality.

Massively parallel sequencing (MPS) offers substantial improvements over current forensic DNA typing methodologies such as increased resolution, scalability, and throughput. The Ion PGM™ is a promising MPS platform for analysis of forensic biological evidence. The system employs a sequencing-by-synthesis chemistry on a semiconductor chip that measures a pH change due to the release of hydrogen ions as nucleotides are incorporated into the growing DNA strands. However, implementation of MPS into forensic laboratories requires a robust chemistry. Ion Torrent's Hi-Q™ Sequencing Chemistry was evaluated to determine if it could improve on the quality of the generated sequence data in association with selected genetic marker targets. The whole mitochondrial genome and the HID-Ion STR 10-plex panel were sequenced on the Ion PGM™ system with the Ion PGM™ Sequencing 400 Kit and the Ion PGM™ Hi-Q™ Sequencing Kit. Concordance, coverage, strand balance, noise, and deletion ratios were assessed in evaluating the performance of the Ion PGM™ Hi-Q™ Sequencing Kit. The results indicate that reliable, accurate data are generated and that sequencing through homopolymeric regions can be improved with the use of Ion Torrent's Hi-Q™ Sequencing Chemistry. Overall, the quality of the generated sequencing data supports the potential for use of the Ion PGM™ in forensic genetic laboratories.

DNA Fingerprinting: A substantial and imperative aid to forensic investigation

Over the last three decades, the DNA profiling is based on a set of core short tandem repeat [STR] loci that are being widely used for forensic DNA testing, which provide sufficient discrimination power for most applications. Today’s forensic DNA tests employ PCR and capillary electrophoresis [CE] based fragment analysis methods to detect length variation in STRs. Presently most of the forensic laboratories are generating biparental autosomal STR based DNA profile on 16 to 20 and uniparental Y STR profile on 17 or 23 STR markers. A variety of commercial kits enable hassle free, fast and accurate multiplex amplification of these core STR loci. With the advanced 6 dye matrix supporting Genetic Analyser 3500/3500Xl, simultaneous amplification of much more STR markers is possible now, which is motivating kit provider companies to increase markers in a single multiplex for increased discrimination power. Besides the increase in number of markers in a single multiplex, the master mix in the preformulated kit is also improved for inhibitor tolerance as well as enabling fast PCR. In the last few years there has been growing interest in DNA phenotyping which is expected to enable investigation in solving blind cases by providing clues in cases where DNA typing fails. However, much more research is required to make this an established technology like DNA fingerprinting. The new arrival in forensic DNA typing is the launch of pre-formulated NGS based multiplex kits, providing option for simultaneous amplification of different types and more number of STR markers along with ancestry based SNPs in a single run, thus besides saving cost and time both, are more informative too. The article reviews diverse variants of DNA fingerprinting technology, its status and application in forensic case work.

Yfiler® Plus amplification kit validation and calculation of forensic parameters for two Austrian populations

With the new 6-dye AmpFISTR® Yfiler® Plus amplification kit (Thermo Fisher Scientific, Waltham, MA, USA) a set of 25 Y-chromosomal short tandem repeat loci (Y-STRs), including seven rapidly mutating Y-STRs (RM Y-STRs), is now available for forensic DNA typing. In this study we present our validation data for the AmpFISTR® Yfiler® Plus amplification kit and show the results of Y-chromosomal typing of 425 unrelated male individuals from two Austrian populations (Salzburg and Upper Austria) with the AmpFISTR® Yfiler® Plus amplification kit. Forensic parameters were calculated and compared for four Y-STR marker sets. We also typed five brother pairs to evaluate the power of discrimination for related individuals. The AmpFISTR® Yfiler® Plus (Yfiler Plus) kit appeared to be unimpaired by typical inhibitors such as hematin and humic acid or by large amounts of female components. An upgrade of analyzed markers resulted in increased discrimination capacity that is crucial for forensic trace analysis.

A Genome-Wide Scan of DNA Methylation Markers for Distinguishing Monozygotic Twins

Identification of individuals within pairs of monozygotic (MZ) twins remains unresolved using common forensic DNA typing technology. For some criminal cases involving MZ twins as suspects, the twins had to be released due to inability to identify which of the pair was the perpetrator. In this study, we performed a genome-wide scan on whole blood-derived DNA from four pairs of healthy phenotypically concordant MZ twins using the methylated DNA immunoprecipitation sequencing technology to identify candidate DNA methylation markers with capacity to distinguish MZ twins within a pair. We identified 38 differential methylation regions showing within-pair methylation differences in all four MZ pairs. These are all located in CpG islands, 17 of which are promoter-associated, 17 are intergenic islands, and four are intragenic islands. Genes associated with these markers are related with cell proliferation, differentiation, and growth and development, including zinc finger proteins, PRRX2, RBBP9, or are involved in G-protein signaling, such as the regulator of G-protein signaling 16. Further validation studies on additional MZ twins are now required to evaluate the broader utility of these 38 markers for forensic use.

A Strategy for Characterization of Single Nucleotide Polymorphisms in a Reference Material

The advent and adoption of next generation sequencing (NGS) is enabling analysis of single nucleotide polymorphisms (SNPs) at an unprecedented scale, limited primarily by multiplexing during the PCR amplification based enrichment step used for forensic applications. Since only a single nucleotide is assayed, PCR primers may be designed to generate small amplicons, making SNP markers well-suited to forensic DNA typing. Carefully selected panels of SNP markers have been previously established for forensic applications such as one-to-one matching, estimating biogeographical ancestry, and predicting externally visible phenotype [1–6]. To support the implementation of SNPs in forensic DNA analysis, NIST has examined the HID-Ion AmpliSeq Identity Panel and the HID-Ion AmpliSeq Ancestry Panel for the Ion Torrent Personal Genome Machine (PGM). In total, over 289 SNP markers have been typed. NIST intends to use a strategy combining NGS on orthogonal platforms and Sanger sequencing for characterizing the SNP markers for varying levels of confidence. The outcome will be to report only the SNP allele calls, analogous to the mitochondrial sequence variants in NIST Standard Reference Material (SRM) 2392, and not the subsequent application of the information (e.g. prediction of ancestry or phenotype).

Evaluation of the Illumina® Beta Version ForenSeq™ DNA Signature Prep Kit for use in genetic profiling

While capillary electrophoresis-based technologies have been the mainstay for human identity typing applications, there are limitations with this methodology’s resolution, scalability, and throughput. Massively parallel sequencing (MPS) offers the capability to multiplex multiple types of forensically-relevant markers and multiple samples together in one run all at an overall lower cost per nucleotide than traditional capillary electrophoresis-based methods; thus, addressing some of these limitations. MPS also is poised to expand forensic typing capabilities by providing new strategies for mixture deconvolution with the identification of intra-STR allele sequence variants and the potential to generate new types of investigative leads with an increase in the overall number and types of genetic markers being analyzed. The beta version of the Illumina ForenSeq DNA Signature Prep Kit is a MPS library preparation method with a streamlined workflow that allows for targeted amplification and sequencing of 63 STRs and 95 identity SNPs, with the option to include an additional 56 ancestry SNPs and 22 phenotypic SNPs depending on the primer mix chosen for amplification, on the MiSeq desktop sequencer (Illumina). This study was divided into a series of experiments that evaluated reliability, sensitivity of detection, mixture analysis, concordance, and the ability to analyze challenged samples. Genotype accuracy, depth of coverage, and allele balance were used as informative metrics for the quality of the data produced. The ForenSeq DNA Signature Prep Kit produced reliable, reproducible results and obtained full profiles with DNA input amounts of 1ng. Data were found to be concordant with current capillary electrophoresis methods, and mixtures at a 1:19 ratio were resolved accurately. Data from the challenged samples showed concordant results with current DNA typing methods with markers in common and minimal allele drop out from the large number of markers typed on these samples. This set of experiments indicates the beta version of the ForenSeq DNA Signature Prep Kit is a valid tool for forensic DNA typing and warrants full validation studies of this MPS technology.

Developmental validation of the GlobalFiler® Express PCR Amplification Kit: A 6-dye multiplex assay for the direct amplification of reference samples

In order to increase the power of discrimination, reduce the possibility of adventitious matches, and expand global data sharing, the CODIS Core Loci Working Group made a recommendation to expand the CODIS core loci from the “required” 13 loci to 20 plus three additional “highly recommended” loci. The GlobalFiler® Express Kit was designed to incorporate all 20 required and 3 highly recommended loci along with a novel male-specific Y insertion/deletion marker. The GlobalFiler® Express Kit allows simultaneous amplification of the following loci: D3S1358, vWA, D16S539, CSF1PO, TPOX, Yindel, AMEL, D8S1179, D21S11, D18S51, DYS391, D2S441, D19S433, TH01, FGA, D22S1045, D5S818, D13S317, D7S820, SE33, D10S1248, D1S1656, D12S391, and D2S1338. The kit enables direct amplification from blood and buccal samples stored on paper or swab and the chemistry features an optimized PCR protocol that yields time to results in less than an hour. Developmental validation testing followed SWGDAM guidelines and demonstrated the quality and robustness of the GlobalFiler® Express Kit over a number of variables. The validation results demonstrate that the 24-locus multiplex kit is a robust and reliable identification assay as required for forensic DNA typing and databasing.

A comparison of four methods for PCR inhibitor removal

Biological samples collected from the crime scenes often contain some compounds that can inhibit the polymerase chain reaction (PCR). The removal of PCR inhibitors from the extracts prior to the PCR amplification is vital for successful forensic DNA typing. This paper aimed to evaluate the ability of four different methods (PowerClean® DNA Clean-Up kit, DNA IQ™ System, Phenol–Chloroform extraction and Chelex®-100 methods) to remove eight commonly encountered PCR inhibitors including: melanin, humic acid, collagen, bile salt, hematin, calcium ions, indigo and urea. Each of these PCR inhibitors was effectively removed by the PowerClean® DNA Clean-Up kit and DNA IQ™ System as demonstrated by generating more complete short tandem repeat (STR) profiles from the cleaned up inhibitor samples than from the raw inhibitor samples. The Phenol–Chloroform extraction and Chelex®-100 methods, however, could only remove some of eight PCR inhibitors. Our results demonstrated that the PowerClean® DNA Clean-Up kit and DNA IQ™ System were very effective for the removal of known PCR inhibitors that are routinely found in DNA extracts from forensic samples.

Ancient DNA and Forensics Mutual Benefits a Practical Sampling and Laboratory Guide Through a Virtual Ancient DNA Study

Genetic information discovered, characterized for and used in forensic case-works and anthropology has shown to be also highly useful and relevant in investigating human remains from archaeological findings. By technical means, forensic and aDNA (ancient Deoxyribonucleic acid) analyses are well suited to be done using the same laboratory infrastructures and scientific expertise referring to sampling, sample protection, sample processing, contamination control as well as requiring analogous technical know how and knowledge on reading and interpreting DNA encoded information. Forensic genetics has significantly profited from aDNA-related developments (and vice versa, of course!), especially, when it comes to the identification of unknown human remains referring to the detection limit. Additionally the tremendous developments of analyzing chemistry and kits as well as instruments in forensics opened the whole panel of reading human and nonhuman DNA for historians and archaeologists but also for anthropologists. Ancient DNA / molecular archaeology, however, is not limited to the comparatively restrictive set of information as usually employed in forensic case work analyses but can also be applied to phenotypical markers, ethno-related genotypes or pathological features.In this review the authors give a general overview on the field of ancient DNA analysis focussing of the potentials and limits, fields of application, requirements for samples, laboratory setup, reaction design and equipment as well as a brief outlook on current developments, future perspectives and potential cross links with associated scientific disciplines.Key words: Human DNA, Ancient DNA, Forensic DNA typing, Molecular archaeology, Application.

An Investigation of PCR Inhibition Using Plexor®‐Based Quantitative PCR and Short Tandem Repeat Amplification

A common problem in forensic DNA typing is PCR inhibition resulting in allele dropout and peak imbalance. In this paper, we have utilized the Plexor(®) real-time PCR quantification kit to evaluate PCR inhibition. This is performed by adding increasing concentrations of various inhibitors and evaluating changes in melt curves and PCR amplification efficiencies. Inhibitors examined included calcium, humic acid, collagen, phenol, tannic acid, hematin, melanin, urea, bile salts, EDTA, and guanidinium thiocyanate. Results were plotted and modeled using mathematical simulations. In general, we found that PCR inhibitors that bind DNA affect melt curves and CT takeoff points while those that affect the Taq polymerase tend to affect the slope of the amplification curve. Mixed mode effects were also visible. Quantitative PCR results were then compared with subsequent STR amplification using the PowerPlex(®) 16 HS System. The overall results demonstrate that real-time PCR can be an effective method to evaluate PCR inhibition and predict its effects on subsequent STR amplifications.

Trumping Communitarianism: Crime Control and Forensic DNA Typing and Databasing in Singapore

Liberalism and communitarianism have figured prominently in discussions of how to govern forensic DNA practices (forensic DNA typing and databasing). Despite the prominence of these two political philosophies and their underlying values, no studies have looked at the governance of forensic DNA practices in a nondemocratic country governed by a communitarian logic. To fill this lacuna in the literature, this article considers Singapore as an authoritarian state governed by a communitarian philosophy. The article highlights basic innovations and technologies of forensic DNA practices and articulates a liberal democratic version of “biolegality” as described by Michael Lynch and Ruth McNally. It goes on to consider briefly various (political) philosophies (liberalism and communitarianism) and law enforcement models (due process and crime control models). The main part of the article records the trajectory, and hence biolegal progress, of forensic DNA practices in Singapore and compares it with trajectories in England and the United States. The article concludes that Singapore's forensic DNA practices are organized according to the crime control model and therefore safety and the war against crime and terrorism trump individual rights and legal principles such as privacy, bodily integrity, proportionality, presumption of innocence. and onus of proof.

Forensic DNA typing strategy of degraded DNA on discarded cigarette ends using the AmpFℓSTR® Identifiler®, Identifiler® Plus and MiniFiler™ PCR amplification kits.

DNA left on a forensic sample is often prone to degradation, especially if left to the elements. To maximize the chance of retrieving the most information from such compromised DNA, an appropriate profiling scheme using the available technologies needs to be devised. In this study, a total of 62 cigarette ends collected under different conditions of environmental exposure were employed to test the effectiveness of three DNA amplification kits, namely the Applied Biosystems™ AmpFℓSTR® Identifiler®, Identifiler® Plus and MiniFiler™ PCR Amplification Kits, in the profiling of such compromised DNA. We demonstrated that Identifiler® Plus could substitute Identifiler® to improve the effectiveness of profiling for those inhibited cigarette samples. MiniFiler™, on the other hand, could supplement Identifiler®/Identifiler® Plus profiles and provide additional genetic information to enhance the evidential value of the samples, especially for those that have suffered from DNA degradation to a greater extent. The findings in this work allowed us to propose a DNA profiling strategy as follow: 1) samples yielding complete Identifiler®/Identifiler® Plus profiles require no further testing with MiniFiler™; 2) samples yielding partial single-source profiles to be tested with MiniFiler™ to add genetic information; 3) samples yielding no results are unlikely to yield any results with MiniFiler™.

Utilizing DNA analysis to combat the world wide plague of present day slavery – trafficking in persons

A study was conducted to determine if modern forensic DNA typing methods can be properly employed throughout the world with a final goal of increasing arrests, prosecutions, and convictions of perpetrators of modern day trafficking in persons while concurrently reducing the burden of victim testimony in legal proceedings. Without interruption of investigations, collection of samples containing DNA was conducted in a variety of settings. Evidentiary samples were analyzed on the ANDE Rapid DNA system. Many of the collected swabs yielded informative short tandem repeat profiles with Rapid DNA technology.

Forensic DNA Typing of Old Skeletal Remains Using AmpFlSTR®Identifiler® PCR Amplification Kit

Background: In this study DNA typing of old skeletal remains was improved through AmpFlSTR®Identifiler®PCR amplification kit using different approaches. Methodology: DNA extraction was carried out by silica columns based total demineralization extraction method.DNA quantification was carried out by Real Time PCR. DNA amplification was carried out by using AmpFlSTR®Identifiler® PCR amplification kit with modified conditions. Capillary electrophoresis and Data analysis were carried out by Genetic Analyzer 3130 (ABI) and GeneMapper ID software version 3.2. Results: DNA was detected in 17 out of 24 skeletal remains. Among them, in 7 samples DNA was in the range of 1-10 pg/µL, in 4 samples it was in the range of 22-69 pg/µL and in 6 samples the DNA was in the range of >100 pg/ µL. The CT value (<30) of 40 cycles indicated that the PCR inhibitors were removed during DNA extraction method. Promising results were obtained by increasing the number of PCR cycles from standard 28 to 33 instead of 32 in PCR reaction. Finally it was observed that consensus approach produced reliable and reproducible DNA profiles from old skeletal remains. Conclusions: Forensic DNA typing of old skeletal remains, through a multiplex AmpFlSTR®Identifiler® PCR amplification kit, is improved by using: a highly effective DNA extraction method, modified and optimized PCR conditions, increasing sensitivity of PCR amplification and consensus approach

Development of a 24-locus multiplex system to incorporate the core loci in the Combined DNA Index System (CODIS) and the European Standard Set (ESS)

The 24-locus multiplex system allows co-amplification and fluorescent detection of 24 loci (23 STR loci and Amelogenin), including STR loci in the Combined DNA Index System (CODIS) and the ESS (European Standard Set) as well as five additional loci (D2S1338, D6S1043, D19S433, Penta D and Penta E) commonly used in commercial kits. It facilitates data sharing and minimizes adventitious matches within national or between international DNA databases. Additionally, the system can amplify directly from blood and buccal samples spotted on filter paper and swabs and reduce the cycling time to less than one hour and a half. Primers, internal size standard, allelic ladders and matrix standard set were designed and created in-house with a design strategy to work in this multiplex. Developmental validation experiments followed the Scientific Working Group on DNA Analysis Methods (SWGDAM) and the Chinese National Standard (GA/T815-2009) guidelines. The system was evaluated by species specificity, sensitivity, stability, precision and accuracy, case-type samples, population, mixture and PCR-based studies. The results demonstrate that the 24-locus multiplex system is a robust and reliable identification assay as required for forensic DNA typing and databasing.

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%).

Polymorphisms analysis and evaluation of five non-CODIS STR loci in a population sample of immigrants living in Northern Italy

ENFSI recently introduced in forensic DNA typing five new STRs loci (D10S1248, D22S1045, D2S441, D1S1656, D12S391) not included in CODIS. It is necessary to obtain data regarding allele frequencies for these five loci in different populations, allowing their use in forensic cases. In this study two groups of individuals of two of the main ethnic groups living in Northern Italy, the Albanians and the Indo-Pakistanis, were typed using the commercial kit AmpFlSTR® NGM; allelic frequencies and forensic parameters were calculated.