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DNA profiling of short tandem repeats (STRs) is the primary method for genotyping forensic samples. However, degraded DNA and trace samples are still major problems for commercial 5- or 6-dye STR kits. In order to improve the performance of this method, we developed a novel 8-dye STR multiplex system containing 18 autosomal loci (D3S1358, D1S1656, TPOX, D16S539, vWA, D6S1043, D2S1338, CSF1PO, D19S433, D7S820, FGA, D8S1179, D5S818, D13S317, TH01, D21S11, D12S391, and PentaD) and the sex-determining locus Amelogenin, with all fragments smaller than 330 bases. Validation was carried out as recommended by the Scientific Working Group on DNA Analysis Methods. The results showed that complete profiles were obtainable when the input DNA was as low as 0.0625 ng. Full profiles were obtained even in the presence of inhibitors such as humic acid (

This paper describes the development and validation of a novel 31-locus, 6-dye STR multiplex system which is designed to meet the needs of the rapidly growing Chinese forensic database. This new assay combines 20 extended-CODIS core loci (D3S1358, D5S818, TPOX, CSF1PO, TH01, vWA, D7S820, D21S11, D8S1179, D18S51, D16S539, D13S317, FGA, D1S1656, D2S441, D2S1338, D10S1248, D12S391, D19S433 and D22S1045), 9 highly polymorphic loci in Chinese Han population (D3S3045, D6S1043, D6S477, D8S1132, D10S1435, D15S659, D19S253, Penta D and Penta E) and two gender determining markers, amelogenin and Y-Indel, which could amplify DNA from extracts, as well as direct amplification from substrates. To demonstrate the suitability for forensic applications, this system was validated by precision and accuracy evaluation, concordance tests, case sample tests, sensitivity, species specificity, stability, stutter calculation and DNA mixtures, according to the guidelines described by the Scientific Working Group on DNA Analysis Methods (SWGDAM) and regulations published by the China Ministry of Public Security. The validation results indicate the robustness and reliability of this new system, and it could be a potentially helpful tool for human identification and paternity testing in the Chinese population, as well as facilitating global forensic DNA data sharing. Additional supporting information may be found in the online version of this article at the publisher's web-site. Color online: See article online to view Figs. 1-5 and 7 in color. This article is protected by copyright. All rights reserved.

During a DNA database construction and population study in China we observed a special genotype at D S locus which was misjudged by seven out of ten different STR multiplex systems Allele typing results acquired by using ten diverse STR multiplex kits PowerPlex reg Fushion C nbsp PowerPlex reg nbsp PowerPlex reg nbsp ACGU reg EX nbsp AppliedBio reg HuaXiaBaijin nbsp SureID reg PanGlobal nbsp GoldeneyeTM A nbsp GoldenEyeTM nbsp A nbsp AppliedBio reg GlobalFiler HuaDa reg YanHuagn and then analyzed by GeneMapper reg software In this paper we conclude the reasons for the misjudgment of this allele as well as how to reduce these kinds of errors during STR analysis

DNA-based human identity testing is conducted by comparison of PCR-amplified polymorphic Short Tandem Repeat (STR) motifs from a known source with the STR profiles obtained from uncertain sources. Samples such as those found at crime scenes often result in signal that is a composite of incomplete STR profiles from an unknown number of unknown contributors, making interpretation an arduous task. To facilitate advancement in STR interpretation challenges we provide over 25,000 multiplex STR profiles produced from one to five known individuals at target levels ranging from one to 160 copies of DNA. The data, generated under 144 laboratory conditions, are classified by total copy number and contributor proportions. For the 70% of samples that were synthetically compromised, we report the level of DNA damage using quantitative and end-point PCR. In addition, we characterize the complexity of the signal by exploring the number of detected alleles in each profile.

Performance of PowerPlex Fusion 6C kit (PP F6C) was assessed in 374 unrelated individuals belonging to Madhya Pradesh, an Indian state. The study evaluated the forensic parameters for the loci included in PP F6C Multiplex System. The combined discrimination power (CPD) and combined exclusion power (CPE) were 1 and 0.999999995, respectively, for all 23 autosomal STR loci. SE33 showed the greatest power of discrimination (0.990) in the studied population, whereas TPOX showed the lowest (0.843). The availability of three Y-STR loci in the Multiplex System is suitable for assessing male contribution and amelogenin deletion in a single Multiplex PCR simultaneously. The study also presents the first global report on polymorphism in the Indian population on SE 33 autosomal STR loci and PP Fusion 6C Multiplex System. The results revealed that the studied STR Multiplex System is highly polymorphic and suitable for forensic purposes.

To increase the discrimination power of human identification in forensic and to evaluate expanded short tandem repeat (STR) loci, we examined a Korean sample population of 2000 unrelated individuals using both GlobalFiler™ PCR Amplification kit and PowerPlex® Fusion System. Allele frequencies for the 20 STR loci (D3S1358, vWA, D16S539, CSF1PO, TPOX, D8S1179, D21S11, D18S51, D2S441, D19S433, TH01, FGA, D22S1045, D5S818, D13S317, D7S820, D10S1248, D1S1656, D12S391, and D2S1338) were calculated. Allele frequencies of the 20 STR loci would be useful for personal identification and paternity testing in forensics and as a standard reference database in Korea.

Short tandem repeats (STRs) are hyper-mutable sequences in the human genome. They are often used in forensics and population genetics and are also the underlying cause of many genetic diseases. There are challenges associated with accurately determining the length polymorphism of STR loci in the genome by next-generation sequencing (NGS). In particular, accurate detection of pathological STR expansion is limited by the sequence read length during whole-genome analysis. We developed TREDPARSE, a software package that incorporates various cues from read alignment and paired-end distance distribution, as well as a sequence stutter model, in a probabilistic framework to infer repeat sizes for genetic loci, and we used this software to infer repeat sizes for 30 known disease loci. Using simulated data, we show that TREDPARSE outperforms other available software. We sampled the full genome sequences of 12,632 individuals to an average read depth of approximately 30× to 40× with Illumina HiSeq X. We identified 138 individuals with risk alleles at 15 STR disease loci. We validated a representative subset of the samples (n = 19) by Sanger and by Oxford Nanopore sequencing. Additionally, we validated the STR calls against known allele sizes in a set of GeT-RM reference cell-line materials (n = 6). Several STR loci that are entirely guanine or cytosines (G or C) have insufficient read evidence for inference and therefore could not be assayed precisely by TREDPARSE. TREDPARSE extends the limit of STR size detection beyond the physical sequence read length. This extension is critical because many of the disease risk cutoffs are close to or beyond the short sequence read length of 100 to 150 bases.

The PowerPlex Fusion 6C system is a six-dye STR multiplex that allows co-amplification and fluorescent detection of 27 loci, including Amelogenin, 23 autosomal STR loci and 3 Y chromosome STR loci....

Improvised explosive devices (IEDs) such as pipe bombs are weapons used to detrimentally affect people and communities. A readily accessible brand of exploding targets called Tannerite® has been identified as a potential material for abuse as an explosive in pipe bombs. The ability to recover and genotype DNA from such weapons may be vital in the effort to identify suspects associated with these devices. While it is possible to recover DNA from post-blast fragments using short tandem repeat markers (STRs), genotyping success can be negatively affected by low quantities of DNA, degradation, and/or PCR inhibitors. Alternative markers such as insertion/null (INNULs) and single nucleotide polymorphisms (SNPs) are bi-allelic genetic markers that are shorter genomic targets than STRs for amplification, which are more likely to resist degradation. In this study, we constructed pipe bombs that were spiked with known amounts of biological material to: 1) recover "touch" DNA from the surface of the device, and 2) recover traces of blood from the ends of wires (simulated finger prick). The bombs were detonated with the binary explosive Tannerite® using double-base smokeless powder to initiate the reaction. DNA extracted from the post-blast fragments was quantified with the Quantifiler® Trio DNA Quantification Kit. STR analysis was conducted using the GlobalFiler® Amplification Kit, INNULs were amplified using an early-access version of the InnoTyper™ 21 Kit, and SNP analysis via massively parallel sequencing (MPS) was performed using the HID-Ion Ampliseq™ Identity and Ancestry panels using the Ion Chef and Ion PGM sequencing system. The results of this study showed that INNUL markers resulted in the most complete genetic profiles when compared to STR and SNP profiles. The random match probabilities calculated for samples using INNULs were lower than with STRs when less than 14 STR alleles were reported. These results suggest that INNUL analysis may be well suited for low-template and/or degraded DNA samples, and may be used to supplement incomplete or failed STR analysis. Human identification using SNP analysis via MPS showed variable success with low-level post-blast samples in this study (

Marijuana (Cannabis sativa L.) is a plant cultivated and trafficked worldwide as a source of fiber (hemp), medicine, and intoxicant. The development of a validated method using molecular techniques such as short tandem repeats (STRs) could serve as an intelligence tool to link multiple cases by means of genetic individualization or association of cannabis samples. For this purpose, a 13 loci STR multiplex method was developed, optimized, and validated according to relevant ISFG and SWGDAM guidelines. The STR multiplex consists of 13 previously described C. sativa STR loci: ANUCS501, 9269, 4910, 5159, ANUCS305, 9043, B05, 1528, 3735, CS1, D02, C11, and H06. A sequenced allelic ladder consisting of 56 alleles was designed to accurately genotype 101 C. sativa samples from three seizures provided by a U.S. Customs and Border Protection crime lab. Using an optimal range of DNA (0.5–1.0 ng), validation studies revealed well-balanced electropherograms (inter-locus balance range: 0.500–1.296), relatively balanced heterozygous peaks (mean peak height ratio of 0.83 across all loci) with minimal artifacts and stutter ratio (mean stutter of 0.021 across all loci). This multi-locus system is relatively sensitive (0.13 ng of template DNA) with a combined power of discrimination of 1 in 55 million. The 13 STR panel was found to be species specific for C. sativa; however, non-specific peaks were produced with Humulus lupulus. The results of this research demonstrate the robustness and applicability of this 13 loci STR system for forensic DNA profiling of marijuana samples.

The EX27 System is a 6-dye (i.e., FAM, HEX, TAMAR, ROX, VIG, and SIZ-500) kit that combines the 24 autosomal STR loci (i.e., D3S1358, D13S317, D7S820, D16S539, D1S1656, Penta E, TPOX, TH01, D2S1338, CSF1PO, Penta D, D10S1248, D19S433, vWA, D21S11, D18S51, D6S1043, D8S1179, D5S818, D12S391, FGA, D22S1045, D2S441, SE33) with a Y-STR locus (DYS391), an Indel site (YIndel) and Amelogenin, which is designed to amplify DNA from extracts as well as direct amplification from substrates. The new system contains most of the widely used autosomal STR loci around the world and is sensitive to the male component in mixtures and is more accurate in gender determination owing to the DYS391 and YIndel.To demonstrate the suitability for personal identification and parentage testing, the system was validated for sensitivity of detection, species specificity, inhibitor tolerance, DNA mixtures, reproducibility study, and concordance studies based on the SWGDAM developmental validation guidelines. In view of the results, the EX27 System is a robust and reliable amplification kit which can be used for human identification testing.

Microreader™ 23sp ID system is a new 23-plex STR genotyping system that amplified 21 non-CODIS STR loci (D6S477, D18S535, D19S253, D15S659, D11S2368, D20S470, D1S1656, D22-GATA198B05, D7S3048, D8S1132, D4S2366, D21S1270, D13S325, D9S925, D3S3045, D14S608, D10S1435, D12S391, D2S1338, D17S1290 and D5S2500), one CODIS STR locus (D16S539) and the amelogenin locus in one reaction. Microreader™ 23sp ID system was validated according to the guidelines of "Validation Guidelines for DNA Analysis Methods (2012)" described by the Scientific Working Group on DNA Analysis Methods (SWGDAM), including PCR-based studies, sensitivity study, precision and accuracy evaluation, stutter percentage and peak height ratio, inhibitors, species specificity and DNA mixture studies. Our results suggested that Microreader™ 23sp ID system is a useful tool for identification and parentage testing.

Short tandem repeat (STR) is widely used for DNA profiling in forensic sciences for its stable inheritance. Genomic variations in STR loci may affect the results of the genotyping. In this study, using STR profiling and genome-wide chromosomal microarray assay, we detected the incidence of uniparental disomy or copy-neutral loss of heterozygosity (LOH) in a case of a parental testing, which altered the genotype of three commonly used STR markers including D2S1338, D2S441 and D2S1776. To the best of our knowledge, this is the first time found that LOH affect the genotyping of STR markers commonly used for paternity testing. Our findings demonstrated that the incidence of LOH in the genome may dramatically alter the results of DNA identification, and suggested that genomic structure variation need to be taking into consideration in the DNA identification using STR markers.

According to the Brazilian Federal Police (BFP), the Brazilian Cannabis sativa illicit market is mainly supplied by drugs originated from Paraguay and Northeastern Brazil (Marijuana Polygon region). These two known routes, the increasing indoor cultivations (supported by online market), and drugs from Uruguay are also in BFP's sight. Forensic tools to aid police intelligence were published in the past years. In genetics, microsatellites have gained attention due to their individualization capability. This study aims to evaluate the effectiveness and efficiency of two STR multiplex systems previously proposed in 94 Cannabis sativa samples seized in Brazil. Principal coordinate analyses (PCoA), forensic parameters, and genetic structure analysis were executed. Both panels were effective in individualizing and origin discriminating all samples, and the system proposed in 2015 demonstrated better results. For this marker set, the probability of identity for a random individual is approximately one in 65 billion; also, the PCoA shows a clear genetic distinction among samples according to its origin. Bayesian inference populational structure analysis indicated a significant genetic diversity among seizure groups, matching with its origin. Overall, the STR multiplex systems were able to achieve its purpose in individualizing and differentiating, according to geographic region, Brazilian Cannabis sp. samples.

The HomyGene19+14Y System (HG19+14Y) is a PCR-based amplification kit that enables typing of 18 autosomal short tandem repeat (STR) loci (i.e., CSF1PO, D2S1338, D3S1358, D5S818, D6S1043, D7S820, D8S1179, D12S391, D13S317, D16S539, D18S51, D19S433, D21S11, FGA, Penta E, TPOX, TH01, vWA), 14 widely used Y chromosome STR (Y-STR) loci (Y_GATA_H4, DYS385a/b, DYS389I/II, DYS390, DYS391, DYS392, DYS393, DYS438, DYS439, DYS456, DYS458, DYS635), and amelogenin. This multiplex system was designed for the simultaneous analysis of amelogenin-Y allele mutation, single-source searches, kinship (including familial searching), mixture profiles, international data sharing, and other forensic applications. In this study, the multiplex system was validated for sensitivity, specificity, DNA mixtures, stability, precision, stutter, reproducibility, parallel tests, PCR-based conditions, and population analysis according to the Scientific Working Group on DNA Analysis Methods (SWGDAM) developmental validation guidelines. A total of 212 alleles were detected for the 18 autosomal STR loci among 528 Guangdong Han individuals, and 431 haplotypes were found for 14 Y-STRs among 452 unrelated males. The combined match probability (CMP) of the HG19+14Y System was calculated as 2.39 × 10−29. All the validation results showed that the HG19+14Y System would be a robust, reliable, highly polymorphic, and informative forensic kit.

Massively parallel sequencing (MPS) technology is gaining interest in the forensic community. The capabilities of high throughput and simultaneously analyses of many markers enable MPS as an attractive method for human forensics. Recent studies have demonstrated the successful application of the MPS system to short tandem repeat (STR) typing. However, not only DNA sequence variations in the repeat regions of STR but also in flanking regions are required to facilitate profiles sharing with capillary electrophoresis (CE)-based typing method. In this study, we constructed a multiplex PCR system for the MPS analysis of 10 autosomal STR loci (D13S317, D16S539, D19S433, D2S441, D3S1358, D5S818, D6S1043, D7S820, TH01, TPOX) by designing amplicons in the size range of 168–273 base pairs. Sequencing results from 165 Chinese unrelated individuals demonstrated 11 variations in the flanking regions between amplification primer binding sites and core repeat motifs. In addition, three loci, D13S317, D5S818, and D7S820, displayed variants adjacent to the core repeats and caused discordances between sequence-based and length-based typing results. Four loci (D3S1358, D2S441, D19S433 and D7S820) demonstrated an increased allele number using MPS-based typing. This study demonstrated that STR typing by MPS could provide more genetic information from both repeat and flanking regions of STR loci, thus improving the diversity and discrimination power of the system in forensic detection.

Motivation Microsatellites, also known as short tandem repeats (STRs), are tracts of repetitive DNA sequences containing motifs ranging from two to six bases. Microsatellites are one of the most abundant type of variation in the human genome, after single nucleotide polymorphisms (SNPs) and Indels. Microsatellite analysis has a wide range of applications, including medical genetics, forensics and construction of genetic genealogy. However, microsatellite variations are rarely considered in whole-genome sequencing studies, in large due to a lack of tools capable of analyzing them. Results Here we present a microsatellite genotyper, optimized for Illumina WGS data, which is both faster and more accurate than other methods previously presented. There are two main ingredients to our improvements. First we reduce the amount of sequencing data necessary for creating microsatellite profiles by using previously aligned sequencing data. Second, we use population information to train microsatellite and individual specific error profiles. By comparing our genotyping results to genotypes generated by capillary electrophoresis we show that our error rates are 50% lower than those of lobSTR, another program specifically developed to determine microsatellite genotypes. Availability and Implementation Source code is available on Github: https://github.com/DecodeGenetics/popSTR

The 19 X-STRs multiplex system is a PCR-based amplification kit that facilitates simultaneous amplification of 19 X-chromosomal STR loci (i.e. DXS7423, DXS10148, DXS10159, DXS6809, DXS7424, DXS8378, DXS10164, DXS10162, DXS7132, DXS10079, DXS6789, DXS101, DXS10103,DXS10101, HPTRB, DXS10075, DXS10074, DXS10135, and DXS10134). Eleven loci were extensively used in an Investigator Qiagen Argus X-12 (DXS7423, DXS10148, DXS8378, DXS10162, DXS7132, DXS10079, DXS10103, DXS10101, HPTRB, DXS10074, and DXS10135). In this research, the multiplex system was tested for detection sensitivity, DNA mixtures, inhibitor tolerance and species specificity; SWGDAM Validation Guidelines - Approved December 2012 were followed for the human fluorescent STR multiplex PCR reagent. Samples from 181 unrelated Zhejiang Han individuals (121 males and 60 females) were typed using this multiplex system. The results show that this 19X-STRs multiplex system is a robust and reliable amplification means to facilitate forensic and human identification testing.

DNA-STR genotyping technology has been widely used in forensic investigations. Even with such success, there is a great need to reduce the analysis time. In this study, we established a new rapid 21-plex STR typing system, including 13 CODIS loci, Penta D, Penta E, D12S391, D2S1338, D6S1043, D19S433, D2S441 and Amelogenin loci. This system could shorten the amplification time to a minimum of 90 min and does not require DNA extraction from the samples. Validation of the typing system complied with the Scientific Working Group on DNA Analysis Methods (SWGDAM) and the Chinese National Standard (GA/T815-2009) guidelines. The results demonstrated that this 21-plex STR typing system was a valuable tool for rapid criminal investigation.

Sequencing short tandem repeat (STR) loci allows for determination of repeat motif variations within the STR (or entire PCR amplicon) which cannot be ascertained by size-based PCR fragment analysis. Sanger sequencing has been used in research laboratories to further characterize STR loci, but is impractical for routine forensic use due to the laborious nature of the procedure in general and additional steps required to separate heterozygous alleles. Recent advances in library preparation methods enable high-throughput next generation sequencing (NGS) and technological improvements in sequencing chemistries now offer sufficient read lengths to encompass STR alleles. Herein, we present sequencing results from 183 DNA samples, including African American, Caucasian, and Hispanic individuals, at 22 autosomal forensic STR loci using an assay designed for NGS. The resulting dataset has been used to perform population genetic analyses of allelic diversity by length compared to sequence, and exemplifies which loci are likely to achieve the greatest gains in discrimination via sequencing. Within this data set, six loci demonstrate greater than double the number of alleles obtained by sequence compared to the number of alleles obtained by length: D12S391, D2S1338, D21S11, D8S1179, vWA, and D3S1358. As expected, repeat region sequences which had not previously been reported in forensic literature were identified.

DNA testing of X-chromosomal short tandem repeat (X-STR) polymorphisms has been the focus of attention in several studies, mainly due to its applicability in the investigation of complex kinship cases. Studies of X-STR in analyses of DNA sequences, population studies and DNA testing applications have been reported. We performed detection and population genetic study of a novel tetranucleotide X-STR locus in the present study. We identified a unique X-STR locus consisting of two tetranucleotides in Xq28. Although the STR is a simple tetranucleotide, its polymorphism was comparatively high [polymorphism information content (PIC)=0.7140] in Japanese subjects. In addition, the STR varied in structure among ethnic groups. We conclude that this locus will be useful for forensic DNA testing and anthropological studies.

Next Generation Sequencing (NGS) is transforming the landscape of the Short Tandem Repeat (STR) genotyping. NGS determines the length as well as the sequence of each allele, identifies polymorphisms in the repeat or adjacent DNA regions, allows for a greater degree of multiplexing, and generates Gigabases of reads in a single run. An additional step introduced into the DNA typing process with NGS methods is library preparation. The PCR amplicons of the targeted loci are further purified and modified with adapters and sample specific indices prior to sequencing. In this study, two PCR purification methods were used to cleanup amplification reactions prior to library construction: column-based and bead-based technologies. The influence of different PCR purification protocols on the dropout events was examined.

Application of the short tandem repeats (STRs) loci located in the X chromosome has become an efficient tool in forensic kinship testing. The aim of this study is to develop a new multiplex that analysis of 19 X-STRs loci (DXS9895, GATA144D04, DXS10077, DXS10078, DXS10161, DXS10160, DXS981, DXS6800, DXS6803, DXS9898, DXS6801, DXS6799, DXS6797, DXS7133, DXS6804, GATA172D05, DXS8377, DXS10146, and DXS10147) simultaneously in a single reaction and to evaluate the allele and haplotype diversity of this multiplex system in the Chinese Han population. In addition, the sensitivity test showed a complete genotyping profile with DNA as low as 0.25ng. The results indicate that the new 19 X-STRs multiplex system may provide high polymorphism information and could be used as a supplementary tool for kinship testing as well as X chromosome genetic mapping studies in China.

It is known that Cannabis in Brazil could either originate from Paraguay or be cultivated in Brazil. While consumer markets in the North and Northeast regions are maintained by national production, the rest of the country is supplied with Cannabis from Paraguay. However, the Brazilian Federal Police (BFP) has exponentially increased the seizure number of Cannabis seeds sent by mail. For this reason, the aim of the study was to assess the 13-loci short tandem repeat (STR) multiplex system proposed by Houston et al. (2015) to evaluate the power of such markers in individualization and origin differentiation of Cannabis sativa samples seized in Brazil by the BFP. To do so, 72 Cannabis samples seized in Brazil by BFP were analyzed. The principal coordinate analysis (PCoA) and probability identity (PI) analysis were computed. Additionally, the Cannabis samples' genotypes were subjected to comparison by Kruskal-Wallis H, followed by a multiple discriminant analysis (MDA). All samples analyzed revealed a distinct genetic profile. PCoA clearly discriminated the seizure sets based on their geographic origin. A combination of seven loci was enough to differentiate samples' genotypes, and the PI for a random sample is approximately one in 50 billion. The Cannabis samples were 100% correct as classified by Kruskal-Wallis H, followed by an MDA. The results of this study demonstrate that the 13-loci STR multiplex system successfully achieved the aim of sample individualization and origin differentiation and suggest that it could be a useful tool to help BFP intelligence in tracing back-trade routes.

The present investigation assessed the allele frequencies and forensic parameters for the loci included in PowerPlex 21 multiplex system (Promega, USA) in 101 unrelated individuals residing in the state of Gujarat, India. The study likewise introduces the first global report on polymorphism on Penta D and Penta E autosomal STR loci from the population of Gujarat, India. The obtained outcomes in the study revealed that the considered STR multiplex system is highly polymorphic and suitable for forensic genetic analysis.

We report here the first ever global study on genetic polymorphism using a Verifiler PlusTM autosomal STR multiplex system. The study evaluated genetic characteristics of 23 autosomal STRs in 200 unrelated residents of Guna district of Madhya Pradesh, India. Allele frequencies and forensic parameters are reported. Population comparison analysis was also performed using NJ tree and PCA plot. Penta E marker showed highest power of discrimination (0.938) among all 23 studied markers. The study also presents the first ever global forensic assessment in Indian population on D6S1043 marker (PD 0.937). The results demonstrated that all the 23 markers were highly polymorphic and the Verifiler PlusTM kit is suitable for forensic purposes in Indian population.

Marijuana (Cannabis sativa) is the most commonly used illicit substance in the USA. The development of a validated method using Cannabis short tandem repeats (STRs) could aid in the individualization of samples as well as serve as an intelligence tool to link multiple cases. For this purpose, a modified 13-loci STR multiplex method was optimized and evaluated according to ISFG and SWGDAM guidelines. A real-time PCR quantification method for C. sativa was developed and validated, and a sequenced allelic ladder was also designed to accurately genotype 199 C. sativa samples from 11 U.S. Customs and Border Protection seizures. Distinguishable DNA profiles were generated from 127 samples that yielded full STR profiles. Four duplicate genotypes within seizures were found. The combined power of discrimination of this multilocus system is 1 in 70 million. The sensitivity of the multiplex STR system is 0.25 ng of template DNA. None of the 13 STR markers cross-reacted with any of the studied species, except for Humulus lupulus (hops) which generated unspecific peaks. Phylogenetic analysis and case-to-case pairwise comparison of 11 cases using F st as genetic distance revealed the genetic association of four groups of cases. Moreover, due to their genetic similarity, a subset of samples (N = 97) was found to form a homogeneous population in Hardy-Weinberg and linkage equilibrium. The results of this research demonstrate the applicability of this 13-loci STR system in associating Cannabis cases for intelligence purposes.

Short tandem repeat (STR) markers are the cornerstone of forensic identity and kinship testing. Markers located on the X and the Y chromosome can complement those found on the autosomes, which are commonly used in laboratories today. The distinctive inheritance pattern of the sex chromosomes affords advantages to the investigation of family pedigrees required by mass disaster victim identification or missing persons cases, as well as mixed samples typically recovered in sexual assault crimes. This review aims to provide an overview of how X and Y STR markers are currently being used in forensic laboratories, including the applications which target their use, the markers and multiplexes facilitating recovery of this genetic information, and the tools available to interpret the resulting data. Emerging research topics are considered as well as issues requiring further study for both marker systems.

X-Chromosome short tandem repeat (STR) typing can complement existing DNA profiling protocols and can also offer useful information in cases of complex kinship analysis. This is the first population study of 8 X-linked STRs in Iraq. The purpose of this work was to provide a basic data of allele and haplotype frequency for x-linked markers and methods that are commonly used to analyze microsatellites, and the subsequent possibilities of using these specifities especially in forensic genetics. FTA® Technology (FTA™ paper DNA extraction) was utilized to extract DNA. Amplification was performed using the Mentype® Argus X-UL PCR amplification kit. Products were detected using ABI PRISMR 3100 Genetic Analyzer (Applied Biosystems). Forensic efficiency parameters showed that DXS7132, DXS7423, DXS8378, HPRTB, DXS10074, DXS10101, DXS10134 and DXS10135 are suitable for forensic application in Iraq. All the analyzed markers were in Hardy-Weinberg equilibrium (HWE); therefore Hardy Weinberg laws could be applied for match probability calculation. Keywords: Allele Frequency, Haplotype Frequency, Iraq, Short Tandem Repeat (STR), X-chromosome

In this study, a new STR 25-plex typing system, including 23 autosomal STRs (D1S1656, D2S1338, D2S441, D3S1358, D5S818, D6S1043, D7S820, D8S1179, D10S1248, D12S391, D13S317, D16S539, D18S51, D19S433, D21S11, D22S1045, CSF1PO, FGA, Penta D, Penta E, TH01, TPOX, vWA) and a Y-STR locus of DYS391 and amelogenin, was developed. The included 24 STRs belonged to the main international DNA databases (CODIS, ISSL, ESS-extended, UCL, GCL and NCIDD) except D6S1043 (specially chosen for Chinese population). Developmental validation indicated that the STR 25-plex typing system was reproducible, accurate, sensitive and robust. The sensitivity testing of the system was such that a full profile was obtainable even with 125pg of human DNA. Specificity testing was demonstrated by the lack of cross-reactivity with a variety of commonly encountered animal species and microbial pool. For the stability testing, full profiles can been obtained with humic acid concentration≤60ng/μL and hematin

Human genomic short tandem repeats (STRs) are specific gene sequences containing base pairs that are repeatedly arranged. From the various methods available for identifying individuals, STR analysis is the method most widely used in forensic science. Conventional polymerase chain reaction (PCR) was used for STR typing, and the PCR products, consisting of amplified STR loci (amplicons) were electrophoresed with a DNA analysis device. About ten STR markers were used as standards for STR characterization and analysis of size. Extensive efforts are currently being made to explore the STR sequence diversity by analyzing multiple chromosomal loci using next generation sequencing (NGS). NGS greatly facilitates STR marker analysis for individual identification and the complete sequencing of any given sample through concurrent high-throughput sequencing of multiple loci. As a result, NGS data are more accurate and comprehensive compared to that in a conventional database. In order to overcome the limitations of the currently used size-based STR analysis method, we have typed the DNA of 13 combined DNA index system (CODIS) STR markers using Ion PGM. This kit, developed by Ion Torrent, enables the analysis of STR alleles and the sequencing of corresponding genes. We then analyzed the alleles using the HID_STR_Genotyper plugin. Through this, we determined the sequence of the allele type 15 at the D3S1358 locus in all NIST SRM 2391b samples. This allowed for the verification of the exact type of allele, which the conventional size-based STR typing methods could not resolve.

To aid DNA identification using 36 short tandem repeat (STR) loci for kinship analysis, likelihood ratio (LR) distributions were estimated using the allele frequency data evaluated for the Japanese population in our previous study. The results revealed that the LR tended to be higher when kinship analysis was performed using the 36 STR loci than when the analysis was performed using Identifiler®, the most commonly used commercial DNA typing kit in Japan, even when a sibship case was analyzed. However, a typing kit targeting 36 STR loci is not suitable for the analysis of damaged DNA. In this study, we developed a novel miniplex DNA identification system targeting 7 STR loci (D3S1744, D5S818, D8S1179, D10S2325, Penta D, Penta E, and vWA) that was optimized for use in combination with MiniFiler™ for the Japanese population. The combined matching probability of the MiniFiler plus miniplex system was 4.8×10(-19), which is lower than that of Identifiler (4.3×10(-17)). All expected alleles were detected successfully on DNA isolated from HepG2 human hepatocarcinoma cells by the miniplex system, but no significant signal was observed from a DNA sample isolated from COS-7 African green monkey kidney cells.

STR typing in forensic genetics has been performed traditionally using capillary electrophoresis (CE). However, CE-based method has some limitations: a small number of STR loci can be used; stutter products, dye artifacts and low level alleles. Massively parallel sequencing (MPS) has been considered a viable technology in recent years allowing high-throughput coverage at a relatively affordable price. Some of the CE-based limitations may be overcome with the application of MPS. In this study, a prototype multiplex STR System (Promega) was amplified and prepared using the TruSeq DNA LT Sample Preparation Kit (Illumina) in 24 samples. Results showed that the MinElute PCR Purification Kit (Qiagen) was a better size selection method compared with recommended diluted bead mixtures. The library input sensitivity study showed that a wide range of amplicon product (6-200ng) could be used for library preparation without apparent differences in the STR profile. PCR sensitivity study indicated that 62pg may be minimum input amount for generating complete profiles. Reliability study results on 24 different individuals showed that high depth of coverage (DoC) and balanced heterozygote allele coverage ratios (ACRs) could be obtained with 250pg of input DNA, and 62pg could generate complete or nearly complete profiles. These studies indicate that this STR multiplex system and the Illumina MiSeq can generate reliable STR profiles at a sensitivity level that competes with current widely used CE-based method.

Second-generation sequencing (SGS) using Roche/454 and Illumina platforms has proved capable of sequencing the majority of the key forensic genetic STR systems. Given that Roche has announced that the 454 platforms will no longer be supported from 2015, focus should now be shifted to competing SGS platforms, such as the MiSeq (Illumina) and the Ion Personal Genome Machine (Ion PGM™; Thermo Fisher). There are currently several challenges faced with amplicon-based SGS STR typing in forensic genetics, including current lengths of amplicons for CE-typing and lack of uniform data analysis between laboratories. Thermo Fisher has designed a human identification (HID) short tandem repeat (STR) 10-plex panel including amelogenin, CSF1PO, D16S539, D3S1358, D5S818, D7S820, D8S1179, TH01, TPOX and vWA, where the primers have been designed specifically for the purpose of SGS and the data analysis is supported by Ion Torrent™ software. Hence, the combination of the STR 10-plex and the Ion PGM™ represents the first fully integrated SGS STR typing solution from PCR to data analysis. In this study, four experiments were performed to evaluate the alpha-version of the STR 10-plex: (1) typing of control samples; (2) analysis of sensitivity; (3) typing of mixtures; and (4) typing of biological crime case samples. Full profiles and concordant results between replicate SGS runs and CE-typing were observed for all control samples. Full profiles were seen with DNA input down to 50 pg, with the exception of a single locus drop-out in one of the 100 pg dilutions. Mixtures were easily deconvoluted down to 20:1, although alleles from the minor contributor had to be identified manually as some signals were not called by the Ion Torrent™ software. Interestingly, full profiles were obtained for all biological samples from real crime and identification cases, in which only partial profiles were obtained with PCR-CE assays. In conclusion, the Ion Torrent™ HID STR 10-plex panel offers an all-in-one solution from amplification of STRs and amelogenin, and sequencing to data analysis.

Short tandem repeats (STRs) are found in many prokaryotic and eukaryotic genomes, and are commonly used as genetic markers, in particular for identity and parental testing in DNA forensics. The unstable expansion of some STRs was associated with various genetic disorders (e.g., the Huntington disease), and thus was used in genetic testing for screening individuals at high risk. Traditional STR analyses were based on the PCR amplification of STR loci followed by gel electrophoresis. With the availability of massive whole genome sequencing data, it becomes practical to mine STR profiles in silico from genome sequences. Software tools such as lobSTR and STR-FM have been developed to address these demands, which are, however, built upon whole genome reads mapping tools, and thus may not be sensitive enough. In this paper, we present a standalone software tool STRScan that uses a greedy algorithm for targeted STR profiling in next-generation sequencing (NGS) data. STRScan was tested on the whole genome sequencing data from Venter genome sequencing and 1000 Genomes Project. The results showed that STRScan can profile 20% more STRs in the target set that are missed by lobSTR. STRScan is particularly useful for the NGS-based targeted STR profiling, e.g., in genetic and human identity testing. STRScan is available as open-source software at http://darwin.informatics.indiana.edu/str/ .

Short tandem repeat (STR) expansions have been identified as the causal DNA mutation in dozens of Mendelian diseases. Historically, pathogenic STR expansions could only be detected by single locus techniques, such as PCR and electrophoresis. The ability to use short read sequencing data to screen for STR expansions has the potential to reduce both the time and cost to reaching diagnosis and enable the discovery of new causal STR loci. Most existing tools detect STR variation within the read length, and so are unable to detect the majority of pathogenic expansions. Those tools that can detect large expansions are limited to a set of known disease loci and as yet no new disease causing STR expansions have been identified with high-throughput sequencing technologies.Here we address this by presenting STRetch, a new genome-wide method to detect STR expansions at all loci across the human genome. We demonstrate the use of STRetch for detecting pathogenic STR expansions in short-read whole genome sequencing data with a very low false discovery rate. We further demonstrate the application of STRetch to solve cases of patients with undiagnosed disease and apply STRetch to the analysis of 97 whole genomes to reveal variation at STR loci. STRetch assesses expansions at all STR loci in the genome and allows screening for novel disease-causing STRs.STRetch is open source software, available fromgithub.com/Oshlack/STRetch.

As DNA databases continue to grow and international cooperation increases, forensic STR loci have expanded to increase the discriminatory power and inter-database compatibility. Current capillary electrophoresis (CE) and/or massively parallel sequencing (MPS)-based commercial STR analysis systems reflect such changing trends of expanding STR loci. Due to the general gains of larger multiplexing and the detection of sequence variation, the application of MPS technology to STR analysis has further improved discrimination and is expected to aid in mixture interpretation by increasing the effective number of alleles. However, high-throughput analysis has rarely been reported for forensic DNA databasing. In this study, we present the sequencing results from 250 Korean samples at 23 commonly used STR loci (D1S1656, TPOX, D2S441, D2S1338, D3S1358, FGA, CSF1PO, D5S818, D6S1043, D7S820, D8S1179, D10S1248, TH01, vWA, D12S391, D13S317, Penta E, D16S539, D18S51, D19S433, D21S11, Penta D, and D22S1045) using an in-house assay designed for MPS. All amplicons in the multiplex exhibited a size range of 77 to 217 base pairs, and the barcoded library for the MPS run was easily prepared using a PCR-based library preparation method followed by sequencing on a MiSeq System (Illumina). We compared the STR genotyping results with those obtained using CE and scrutinized the sequence variations in both the targeted STR and flanking regions. MPS results of 23 autosomal STRs were 99.97% concordant with those of CE results. D12S391 and D21S11 exhibited, respectively, the highest number of alleles and genotypes by the MPS analysis. Single nucleotide polymorphisms and insertion and deletions (Indels) were observed in the flanking regions of D1S1656, D2S441, D5S818, D7S820, D13S317, D16S539, D21S11, and Penta D. Consequently, an MPS analysis of an expanded set of STRs, as demonstrated in the population statistics of a Korean population, will be of great practical use in forensic genetics.

This study aimed to develop a short tandem repeat (STR) multiplex system, made up of 22 highly informative STR loci, for application in forensic genetics. The system comprised 21 polymorphic autosomal loci (D3S1358, TH01, D21S11, D18S51, Penta E, D5S818, D13S317, D7S820, D16S539, CSF1PO, Penta D, vWA, D8S1179, TPOX, FGA, D2S441, D17S1301, D19S433, D18S853, D20S482, and D14S1434) and the amelogenin gene locus. Strategies were developed to overcome the challenges involved in creating a multiplex system. Based on the literature and available databases, the STR loci were selected with the aim to obtain discriminatory markers, and followed specific criteria for this purpose. Primers were projected using the Primer3 software, and AutoDimer was used to evaluate possible interactions between them. The 22 selected STR loci were validated individually and jointly, both to assess their sensitivity and to test the efficiency of the multiplex system. Statistical analyses were based on the genetic data of 450 unrelated individuals living in the State of Goias, thus allowing the establishment of the parameters necessary to use this system. A total of 239 alleles were detected for the 22 loci in the set, allowing for a probability of identity of 4.23 x 10-25 to be obtained. The combined power of discrimination was 0.999999999999999999999999 and the combined power of exclusion was 0.99999. Upon complete validation of the entire system, this multiplex assay was considered to be a powerful tool for application in human identification by DNA analysis.

In this study, we describe the developmental validation assay performed on a novel designed STR multiplex system, AGCU 21+1 STR kit. This kit contains a sex-determining locus amelogenin and 21 noncombined DNA index system STR loci, that are, D6S474, D12ATA63, D22S1045, D10S1248, D1S1677, D11S4463, D1S1627, D3S4529, D2S441, D6S1017, D4S2408, D19S433, D17S1301, D1GATA113, D18S853, D20S482, D14S1434, D9S1122, D2S1776, D10S1435, and D5S2500. The 21+1 kit was validated by a series of tests including optimized PCR conditions, sensitivity, precision and accuracy, stutter ratio, DNA mixture, inhibitors, and species specificity according to the revised validation guidelines issued by the Scientific Working Group on DNA Analysis Methods (SWGDAM). Our results in this study show that the kit is a useful tool for forensic application.

Numerous studies demonstrated that STRs have become powerful tools in forensic case work.To profile DNA samples from 104 Turkish males for 13 autosomal, STR markers intended for human identification purposes and to estimate the allele frequency distribution in forensic cases in a Turkish population.Thirteen autosomal STR loci, namely D3S1358, D2S1338, D16S539, D8S1179, D21S11, D18S51, TH01, D13S317, D7S820, CSF1PO, TPOX, D5S818 and FGA, were analysed in a sample of 104 healthy and unrelated Turkish individuals who have been living in the city of İzmir. All loci were amplified by using AmpFlSTR Identifier Kit. Genetic analysis was carried out on an ABI PRISM 310 Genetic Analyser.For each locus, 6-15 alleles were found with frequencies ranging from 0.005-0.514 and heterozygosities ranging from 0.686-0.868. The PIC value was highly significant (0.999).The 13 STR loci in the AmpFlSTR Identifier Kit are suitable for forensic identification and paternity tests due to high heterozygosity. The observed PD value is sufficiently high for human identification purposes. In conclusion, the 13 STR loci seem to be useful markers for personal identification and forensic case work in the Turkish population. The results also demonstrate the importance of region-specific studies.

The idea of developing a new multiplex STR amplification system was conceived in 2011 as an effective way to implement the new European standard set (ESS) of 12 STR markers adopted by The Council of the European Union in 2009 while maintaining an effective compatibility and information exchange with the historical DNA profiles contained in the Spanish national DNA database (around 200,000 DNA profiles) mainly based on the 13 CODIS core STR loci plus D19S433 and D2S1338 markers. With this goal in mind we proposed to test and validate a single STR amplification system for simultaneous analysis of 21 STR markers covering both CODIS and ESS core STR loci plus three additional markers (D19S433, D2S1338, and SE33) also contained in commonly used STR kits and national DNA databases. In 2012, we started the first beta-testing with a 6-dye STR kit prototype containing 24 loci (now known as the GlobalFiler™ PCR Amplification Kit) developed by Life Technologies in response to the CODIS Core Loci Working Group's recommendation to expand the CODIS Core Loci. This prototype included our proposal of 21 autosomal STR markers and two Y-chromosome markers (DYS391 and Y-indel) and maximizes concordance with established databases and previously analyzed samples by maintaining primer sequences of previous Identifiler(®)/NGM SElect™ kits for the 21 STR markers except for TPOX. This paper describes the validation studies conducted with the first commercial available 6-dye STR kit for casework using a 3500 genetic analyzer for fragment detection that included the analysis of the following parameters and aspects: analytical threshold, sensitivity & stochastic threshold, heterozygous balance, stutter threshold, precision and accuracy, repeatability and reproducibility, genotype concordance, DNA mixtures, species specificity, and stability studies with case type samples. The studies demonstrated that the GlobalFiler™ system provided equivalent overall performance to previous forensic STR PCR kits, but with enhanced discrimination power for a better match efficiency that would reduce the chance of adventitious matches during DNA data exchange among national DNA databases.

DNA degradation is a major obstacle in gaining an accurate profile with standard DNA typing technology. Although alternative genotyping strategies such as mini-STRs and SNPs have proven to be more successful in profiling degraded DNA, these approaches also have limitations. Here, we show that locus enrichment by hybridization of degraded genomic DNA with an STR locus-specific biotinylated oligonucleotide is a powerful approach to overcome problems in STR typing of highly degraded DNA. An experimental investigation of factors affecting the efficiency of this method indicates that the choice of primer and molar ratio of primers to genomic DNA are critical factors in improving enrichment of the STR locus before genotyping with multiplex kits. In addition, we find that indirect capture rather than direct capture with magnetic beads yields better enrichment efficiency for STR locus enrichments. Using these strategies, we demonstrate an improvement in STR typing of DNA from cultured cells damaged by exposure to sunlight or UV. We suggest that this approach could be applied to highly degraded forensic samples alone or in combination with mini-STRs.

Short tandem repeat (STR) genotyping methods are widely used for human identity testing applications, including forensic DNA analysis. Samples of DNA containing the length-variant STR alleles are typically separated and genotyped by comparison to an allelic ladder. Here, we describe a newly devised library of cloned STR alleles. The library covers alleles X and Y for the sex-determining locus Amelogenin and 259 other alleles for 22 autosomal STR loci (TPOX, D3S1358, FGA, D5S818, CSF1PO, D7S820, D8S1179, TH01, vWA, D13S317, D16S539, D18S51, D21S11, D2S1338, D6S1043, D12S391, Penta E, D19S433, D11S4463, D17S974, D3S4529 and D12ATA63). New primers were designed for all these loci to construct recombinant plasmids so that the library retains core repeat elements of STR as well as 5'- and 3'-flanking sequences of ∼500 base pairs. Since amplicons of commercial STR genotyping kits and systems developed in laboratories are usually distributed from 50 to

Second generation sequencing (SGS) may revolutionize the field of forensic STR typing. Two of the essential requirements for implementation of an SGS based approach for forensic investigations are (1) establishment of adequate frequency databases and (2) adoption of a new STR nomenclature. We report the STR sequences and allele frequencies of three STR loci: D3S1358, D12S391 and D21S11 in 197 unrelated Danes. We used a new STR nomenclature that depicts the locus name used in forensic genetics, the length of the repeat region divided by the repeat length (typically 4 nucleotides) and detailed sequence information of possible sub-repeats and SNPs within the amplified fragment.

Human nail is an important forensic material for parental testing and individual identification in large-scale disasters. Detection of STR polymorphism from hard tissues generally requires DNA purification, which is technically complicated and time consuming. In the present study, we attempted to detect STR polymorphisms from untreated human nail samples by direct PCR amplification method using the primer mixture supplied with the GenePrint® SilverSTR® III System or the AmpFlSTR® Identifiler® PCR Amplification Kit, and Tks Gflex DNA polymerase known to be effective for amplification from crude samples. A nail fragment measuring approximately 1.5 mm in breadth and 0.5 mm in length was placed directly into a PCR tube, and various PCR conditions were tested. The PCR products were analyzed by denaturing acrylamide gel electrophoresis or CE. Multiple STR polymorphisms were detected successfully. This method that detects STR polymorphisms not only from fresh human fingernails, but also from old nail fragments stored at room temperature for up to 10 years is expected to become a novel DNA analytical method in forensic medicine and genetic studies.

The EX20+4Y System is a polymerase chain reaction (PCR)-based amplification kit that enables typing of 19 autosomal short tandem repeat (STR) loci (i.e., CSF1PO, D13S317, D16S539, D18S51, D21S11, D3S1358, D5S818, D7S820, D8S1179, FGA, TH01, TPOX, vWA, Penta D, Penta E, D2S1338, D19S433, D12S391, D6S1043), four widely used Y chromosome-specific STR (Y-STR) loci (DYS458, DYS456, DYS391, DYS635), and amelogenin. In this study, this multiplex system was validated for sensitivity of detection, DNA mixtures, inhibitor tolerance, species specificity based on the Scientific Working Group on DNA Analysis methods (SWGDAM) developmental validation guidelines, and the Chinese criteria for the human fluorescent STR multiplex PCR reagent. The results show that the EX20+4 System is a robust and reliable amplification kit which can be used for human identification testing.

Short tandem repeat (STR) markers are extensively used for human identification as well as paternity and forensic casework. X-chromosome STR (X-STR) markers are a powerful complementary system especially in deficiency paternity testing. This study presents the development and characterization of a new X-chromosomal short tandem repeat (STR) multiplex using short amplicon (

Over the past decades, main advances in the field of molecular biology, coupled with benefits in genomic technologies, have led to detailed molecular investigations in the genetic diversity generated by researchers. Short tandem repeat (STR) loci are polymorphic loci found throughout all eukaryotic genome. DNA profiling identification, parental testing and kinship analysis by analysis of STR loci have been widely used in forensic sciences since 1993. Malignant tissues may sometimes be the source of biological material for forensic analysis, including identification of individuals or paternity testing. There are a number of studies on microsatellite instability in different types of tumors by comparing the STR profiles of malignant and healthy tissues on the same individuals. Defects in DNA repair pathways (non-repair or mis-repair) and metabolism lead to an accumulation of microsatellite alterations in genomic DNA of various cancer types that result genomic instabilities on forensic analyses. Common forms of genomic instability are loss of heterozygosity (LOH) and microsatellite instability (MSI). In this study, the applicability of autosomal STR markers, which are routinely used in forensic analysis, were investigated in order to detect genotypes in blood samples collected from leukemic patients to estimate the reliability of the results when malignant tissues are used as a source of forensic individual identification. Specimens were collected from 90 acute and 10 chronic leukemia volunteers with oral swabs as well as their paired peripheral blood samples from the Oncology Centre of the Department of Hematology at Istanbul University, during the years 2010-2011. Specimens were tested and compared with 16 somatic STR loci (CSFIPO, THO1, TPOX, vWA, D2S1338, D3S1358, D5S818, D7S820, D8S1179, D13S317, D16S539, D18S51, D19S433, D21S11 and FGA) widely used in forensic identification and kinship. Only two STR instabilities were encountered among 100 specimens. An MSI in the FGA loci and a LOH in the D2S1338 loci were determined in two individuals separately. Our results demonstrate that the use of the biological samples from leukemia patients in forensic identification and kinship testing is questionable, especially if known microsatellite instability is available. Genetic instabilities may alter the STR polymorphism, leading to potential errors on forensic identification of individuals. Therefore, typing of autosomal STRs from leukemia patients should be performed with both healthy and malignant tissue samples of individual as references.

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.

Several commercial multiplex PCR kits for the amplification of short tandem repeat (STR) loci have been extensively applied in forensic genetics. Consequently, large numbers of samples have been genotyped, and the number of discordant genotypes observed has also increased. We observed allele dropout with two novel alleles at the STR loci TH01 and D13S317 during paternity testing using the AmpFℓSTR Identifiler PCR Amplification Kit. The lost alleles reappeared when alternative PCR primer pairs were used. A sequence analysis revealed a G-to-A substitution 82 bases downstream of the last TCAT motif of the repeat region at the TH01 locus (GenBank accession: D00269) and a G-to-T substitution 90 bases upstream of the first TATC motif of the repeat region at the D13S317 locus (GenBank accession: G09017). The frequencies of these two point mutations were subsequently investigated in the Chinese population using sequence-specific primer PCR (SSP-PCR), but neither of these mutations was detected in any of the samples tested. In addition, the DNA samples in which the mutations were identified were amplified to type the point mutations by SSP-PCR to determine the corresponding STR alleles at the two loci. Subsequently, the amplified PCR products with different point mutations and STR repeat numbers were directly sequenced because this strategy overcomes the appearance overlapping peaks generated by different STR alleles and accurately characterizes genotypes. Thus, our findings not only provide useful information for DNA databases and forensic identification but also establish an effective strategy for typing STR alleles with primer binding site mutations.