X-chromosomal Short Tandem Repeats Research Articles

Investigation of 12 X-STR loci in Mongolian and Eastern Han populations of China with comparison to other populations

Due to the unique inheritance pattern, X-chromosomal short tandem repeats (X-STRs) have several advantages in complex kinship cases, such as deficiency cases or grandparent-grandchild and half-sisters testing. In our study, 541 unrelated individuals gathered from Mongolian and Eastern Chinese Han populations were successfully genotyped using the Investigator Argus X-12 kit. We calculated allele/haplotype frequencies and other forensic parameters of the two populations and further explored their genetic distance with already published Chinese populations and six global populations. Our results showed that the 12 X-STR markers were highly informative in the two populations when compared with nine other Chinese populations: significant differences were found at several loci. Geographically neighboring populations or different ethnic groups within the same area appeared to have closer evolutionary relationships. We also analyzed population genetic structure by performing clustering with the STRUCTURE program and Principal Coordinate Analysis (PCoA), and we found that the Chinese and other populations enrolled in this study could be distinguished. Furthermore, Mongolian males were distinguishable from the other studied males by a moderate genetic distance. Our study also expanded the X-STR database, which could facilitate the appropriate application of the 12 X-STR markers in the forensic field in China.

Expanded Croatian 12 X-STR loci database with an overview of anomalous profiles

In order to implement X-chromosome short tandem repeat (X-STR) typing into routine forensic practice, reference database of a given population should be established. Therefore we extended already published data with additional 397 blood samples from unrelated Croatian citizens, and analyzed the total of 995 samples (549 male and 446 female) typed by Investigator® Argus X-12 Kit. To test genetic homogeneity of consecutively processed five historic-cultural regions covering the entire national territory, we calculated pairwise Fst genetic distances between regions based on allele and full haplotype frequencies. Since the comparison did not yield any statistically significant difference, we integrated STR profile information from all regions and used the whole data set to calculate forensic parameters. The most informative marker is DXS10135 (polymorphism information content (PIC = 0.929) and the most informative linkage group (LG) is LG1 (PIC = 0.996). We confirmed linkage disequilibrium (LD) for seven marker pairs belonging to LG2, LG3 and LG4. By including LD information, we calculated cumulative power of discrimination that amounted to 0.999999999997 in females and 0.999999005 in males. We also compared Croatia with 13 European populations based on haplotype frequencies and detected no statistically significant Fst values after Bonferroni correction in any LG. Multi-dimensional scaling plot revealed tight grouping of four Croatian regions amongst populations of southern, central and northern Europe, with the exception of northern Croatia. In this study we gave the first extensive overview of aberrant profiles encountered during Investigator® Argus X-12 typing. We found ten profiles consistent with single locus duplication followed by tetranucleotide tract length polymorphism. Locus DXS10079 is by far the most frequently affected one, presumably mutated in eight samples. We also found four profiles consistent with X-chromosome aneuploidy (three profiles with XXX pattern and one profile with XXY pattern). In conclusion, we established integral forensic Croatian X-chromosome database, proved forensic pertinence of Investigator® Argus X-12 Kit for the entire Croatian population and identified locus DXS10079 as a potential duplication hotspot.

A simple method for calculating the likelihood ratio in a kinship test using X-chromosomal markers incorporating linkage, linkage disequilibrium, and mutation.

X-chromosomal short tandem repeats (X-STRs) are useful for personal identification and kinship tests. However, it has not yet been fully established how to incorporate linkage and linkage disequilibrium (LD) into the calculation of the likelihood ratio (LR). In this paper, we describe a simple calculation method of LR for X-STRs that incorporated linkage, LD, and mutations. Initially, Japanese population data of 27 X-STRs (DXS6807, DXS9902, DXS6795, DXS6810, DXS10076, DXS10077, DXS10078, DXS10162, DXS10163, DXS10164, DXS7132, DXS981, DXS6800, DXS6803, DXS6809, DXS6789, DXS6799, DXS7424, DXS101, DXS7133, GATA172D05, DXS10103, HPRTB, GATA31E08, DXS8377, DXS10147, and DXS7423) were collected from 748 unrelated individuals to estimate the influence of LD. Significant LD was observed on six pairs of loci. Subsequently, using the population data, a simulation study was performed to evaluate the validity of the present calculation method for LR in cases of father-daughter, full-sisters, paternal half-sisters, maternal half-sisters, and unrelated pairs of females (FD, FS, PHS, MHS, and UR, respectively). As a result, the distribution of LR among FD was completely separated from that among UR. In the sibship test, 98.6% of FS and 98.0% of PHS surpassed the maximum value of UR in combined LR. Even in the FS versus MHS setting, 60.5% of FS had a higher LR than any MHS. We conclude that the present model is powerful in discriminating the relationship and is able to obtain a reasonable LR with fewer computations.

Polymorphism of 8 X-Chromosomal STR loci in Turkish population

In forensic sciences, X-chromosomal short tandem repeats (X-STRs), a complementary marker to the other genetic markers (autosomal, Y-chromosomal or mitochondrial), can be used in complex kinship analysis. Especially when a biological sample is not available from the putative father and samples from paternal relatives could be used instead. In this study eight X-chromosomal STR loci (DXS7132, DXS7423, DXS8378, DXS10074, DXS10101, DXS10134, DXS10135, HPRTB and Amelogenin) were investigated in population samples of 129 unrelated healthy Turkish volunteer [male (n=56), female (n=73)]. X-STRs were amplified in a multiplex PCR reaction with Mentype® Argus X-8 Kit. The separation and detection of PCR products were performed by capillary electrophoresis on a 310 Genetic Analyzer (Applied Biosystems). Statistical analysis was performed using POPgene v.1.32. and Arlequin v3.1 softwareÂ’s. Data was compared with Turkish populations living in Europe (Germany and Denmark) and other populations (Japan, Ghana, Finland, Portugal and Germany). The high genetic distances were observed for the geographically distant populations while no significant differences found between in studied and tested Turkish populations. Results showed that eight STR loci on the X chromosome in Turkish population were found as highly polymorphic and useful for forensic applications.

Allelic and haplotype diversity of 12 X-STRs in the United Arab Emirates

X-chromosomal short tandem repeats (X-STRs) are used to complement autosomal and Y-STRs in complex kinship testing, and can be of potential value when determining trace female DNA in male background. We analyzed extracted and directly-amplified samples of 501 males from the United Arab Emirates and report the forensic statistical parameters of 12 X-STRs and haplotypes of the four previously defined linkage groups using the Investigator Argus X-12 QS kit. Combined PDM, PDF, MEC Desmarais Trio and MEC Desmarais Duo based on allele (and haplotype) frequencies were 0.9999999997 (0.999999996), >0.9999999999 (>0.999999999), 0.999999999 (0.999999996) and 0.9999997 (0.99999994) respectively. No shared profile was observed, and significant linkage disequilibrium was detected only within the four linkage groups. We calculated pairwise genetic distance (FST) between our Emirati sample and 35 populations and find they generally mirror biogeography and historical relationships. We identified 20 distinct off-ladder alleles in seven loci, the majority of which at DXS10148 and DXS10134. Our analysis reveals that the 12 loci are informative and discriminatory in the Emirati population.

Allele and haplotype diversity of 12 X-STRs in Sardinia

The analysis of clusters of tightly linked X-chromosome short tandem repeat (STR) markers can assist the interpretation of complex kinship cases. However, when linkage disequilibrium (LD) is present in the population of origin of tested individuals, haplotype rather than allele frequencies should be used in likelihood calculations. The diversity of twelve X-STRs arranged in four linkage groups (I: DXS10148-DXS10135-DXS8378; II: DXS7132-DXS10079-DXS10074; III: DXS10103-HPRTB-DXS10101; IV: DXS10146-DXS10134-DXS7423) was tested in a Sardinian population sample (n=516) including three open populations from the Northern, Central and Southern part of the island, and three isolates (Benetutti, Desulo, Carloforte). Evidence of LD was detected in Sardinia within each linkage group. Significant differences in haplotype and allele frequency distribution of X-STR markers was seen between isolates and open populations, which on the contrary appeared highly homogeneous.The percentage of Sardinian haplotypes previously unobserved in a similar dataset compiled for the Italian population was: 76.3% (linkage group I), 61.3% (linkage group II), 54.1% (linkage group III), 58.9% (linkage group IV). Significant pairwise genetic differences were seen between mainland Italy, the three Sardinian isolates, and the open population of Southern Sardinia.The study confirms the presence of high levels and complex patterns of LD along the X chromosome in Sardinia, and provides population-specific haplotype data for biostatistical evaluation in kinship testing.

Genetic polymorphisms for 19 X-STR loci of Sichuan Han ethnicity and its comparison with Chinese populations.

X-chromosomal short tandem repeats (X-STRs) can be serviced as a complementary tool in forensic deficiency cases and other complicated kinship identification. To investigate the genetic variation of the western Chinese Han population, genetic polymorphisms of 19 X-STR loci (DXS8378, DXS7423, DXS10148, DXS10159, DXS10134, DXS7424, DXS10164, DXS10162, DXS7132, DXS10079, DXS6789, DXS101, DXS10103, DXS10101, HPRTB, DXS6809, DXS10075, DXS10074 and DXS10135) included in the AGCU X19 PCR amplification kit were obtained from 201 Chinese Han individuals (108 females and 93 males) residing in Sichuan province, western China. A total of 211 alleles were found from the 19 X-STR loci, and 4-22 alleles were found for each locus with the corresponding allele frequencies spanned from 0.0034 to 0.6395. The combined PDF and PDM were 0.9999999999999999999992 and 0.9999999999997, respectively. The combined MECKrüger, MECKishida, MECDesmarais as well as MECDesmarais Duo were 0.999999958110254, 0.999999999996533, 0.999999999996695 and 0.999999992428394, respectively. The number of haplotypes observed in the seven linkage groups varied from 27 to 97 for 108 male individuals with the corresponding haplotype diversities spanned from 0.9424 (DXS7424-DXS101) to 0.9979 (DXS7132-DXS10079-DXS10075-DXS10074). The above-mentioned results indicated that the 19 X-STR loci and the seven linkage groups are highly polymorphic and informative in the Sichuan Han population. Results from population comparisons and phylogenetic analyses demonstrated that genetic heterogeneity widely existed between the Sichuan Han population and Xinjiang minority ethnic groups (Uyghur and Kazakh) and genetic affinity was identified in populations which possessed the same ethno-origin or close geographic origin.

Analyzing an “Off-Ladder” allele at DXS10135 from the AGCU X19 STR kit

X chromosome STRs (X-STRs) have been proven to be an important tool for some complex kinship analyses in recent years. A novel 19 X-STRs multiplex system named as AGCU X19 STR Kit was developed and widely used for population genetics as well as forensic case works. In this study an “Off-ladder” allele between allele 21 and allele 21.1 at DXS10135 has been observed in AGCU X19 STR Kit. The “Off-ladder” allele was about 0.4 bases longer than the allele 21 of allelic ladder of DXS10135 in AGCU X19 STR Kit. To avoid DNA profile misunderstanding or mislabeling, “Off-ladder” allele at DXS10135 was analyzed by sequencing and detected with Investigator Argus X-12 Kit, respectively. Our results showed this “Off-ladder” allele was allele 21 at DXS10135. It was caused by inaccurate allele 21 of allelic ladder of DXS10135 in AGCU X19 STR Kit.

Multiplex PCR for 19 X-chromosomal STRs in Chinese population

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.

Massively parallel sequencing of forensic STRs and SNPs using the Illumina® ForenSeq™ DNA Signature Prep Kit on the MiSeq FGx™ Forensic Genomics System

The ForenSeq™ DNA Signature Prep Kit (ForenSeq Kit) is designed to detect more than 200 forensically relevant markers in a single reaction on the MiSeq FGx™ Forensic Genomics System (MiSeq FGx System), including Amelogenin, 27 autosomal short tandem repeats (A-STRs), 7 X chromosomal STRs (X-STRs), 24 Y chromosomal STRs (Y-STRs) and 94 identity-informative single nucleotide polymorphisms (iSNPs) with the option to contain 22 phenotypic-informative SNPs (pSNPs) and 56 ancestry-informative SNPs (aSNPs). In this study, we evaluated the MiSeq FGx System on three major parts: methodological optimization (DNA extraction, sample quantification, library normalization, diluted libraries concentration, and sample-to-cell arrangement), massively parallel sequencing (MPS) performance (depth of coverage, sequence coverage ratio, and allele coverage ratio), and ForenSeq Kit characteristics (repeatability and concordance, sensitivity, mixture, stability and case-type samples). Results showed that quantitative polymerase chain reaction (qPCR)-based sample quantification and library normalization and the appropriate number of pooled libraries and concentration of diluted libraries provided a greater level of MPS performance and repeatability. Repeatable and concordant genotypes were obtained by the ForenSeq Kit. Full profiles were obtained from ≥100pg input DNA for STRs and ≥200pg for SNPs. A sample with ≥5% minor contributors was considered as a mixture by imbalanced allele coverage ratio distribution, and full profiles from minor contributors were easily detected between 9:1 and 1:9 mixtures with known reference profiles. The ForenSeq Kit tolerated considerable concentrations of inhibitors like ≤200μM hematin and ≤50μg/ml humic acid, and >56% STR profiles and >88% SNP profiles were obtained from ≥200-bp degraded samples. Also, it was adapted to case-type samples. As a whole, the ForenSeq Kit is a well-performed, robust, reliable, reproducible and highly informative assay, and it can fully meet requirements for human identification. Further, sensitive QC indicator and automated sample comparison function in the ForenSeq™ Universal Analysis Software are quite helpful, so that we can concentrate on questionable genotypes and avoid tedious and time-consuming labor to maximum the time spent in data analysis.

X-chromosomal STR-based genetic structure of Sichuan Tibetan minority ethnicity group and its relationships to various groups.

The X-chromosomal short tandem repeats (STRs) with more informative than autosomal STRs in some complicated biological relationships identification due to its specific mode of genetic transmission can be used as a complementary tool in forensic case practices. In this study, we presented the population genetic data of 19 X-STRs, consisting of DXS10174, DXS10075, DXS10079, DXS101, DXS10101, DXS10103, DXS10134, DXS10135, DXS10148, DXS10159, DXS10162, DXS10164, DXS6789, DXS6809, DXS7132, DXS7423, DXS7424, DXS8378, and HPRTB loci, in a sample of 235 individuals of Tibetan nationality from Sichuan province, Southwest China. All 19 X-STR loci were consistent with Hardy-Weinberg equilibrium. The results showed that the combined power of discrimination in females and males are 0.999999999999999999997 and 0.9999999999997, respectively. In addition, the mean paternity exclusion chances based on the formula of MECKrüger, MECKishida, and MECDesmarais as well as MECDesmarais Duo are 0.99999991, 0.9999999999924, 0.9999999999929, and 0.999999985, respectively. In summary, our findings suggested that the AGCU X19 kit can be considered to serve as a high polymorphic information tool for forensic identification and kinship testing in the Sichuan Tibetan population. Furthermore, population genetic structure investigation between Sichuan Tibetan population and other 19 populations using PCA, MDS, and phylogenetic tree illustrated that significant genetic difference was observed between the Sichuan Tibetan and Malay, as well as the Xinjiang Uyghur population.

STRSeq: A catalog of sequence diversity at human identification Short Tandem Repeat loci

The STR Sequencing Project (STRSeq) was initiated to facilitate the description of sequence-based alleles at the Short Tandem Repeat (STR) loci targeted in human identification assays. This international collaborative effort, which has been endorsed by the ISFG DNA Commission, provides a framework for communication among laboratories. The initial data used to populate the project are the aggregate alleles observed in targeted sequencing studies across four laboratories: National Institute of Standards and Technology (N=1786), Kings College London (N=1043), University of North Texas Health Sciences Center (N=839), and University of Santiago de Compostela (N=944), for a total of 4612 individuals. STRSeq data are maintained as GenBank records at the U.S. National Center for Biotechnology Information (NCBI), which participates in a daily data exchange with the DNA DataBank of Japan (DDBJ) and the European Nucleotide Archive (ENA). Each GenBank record contains the observed sequence of a STR region, annotation (“bracketing”) of the repeat region and flanking region polymorphisms, information regarding the sequencing assay and data quality, and backward compatible length-based allele designation. STRSeq GenBank records are organized within a BioProject at NCBI (https://www.ncbi.nlm.nih.gov/bioproject/380127), which is sub-divided into: commonly used autosomal STRs, alternate autosomal STRs, Y-chromosomal STRs, and X-chromosomal STRs. Each of these categories is further divided into locus-specific BioProjects. The BioProject hierarchy facilitates access to the GenBank records by browsing, BLAST searching, or ftp download. Future plans include user interface tools at strseq.nist.gov, a pathway for submission of additional allele records by laboratories performing population sample sequencing and interaction with the STRidER web portal for quality control (http://strider.online).

Curiosities of X chromosomal markers and haplotypes.

Recent progress in forensic genetics has introduced a number of closely located short tandem repeat (STR) markers on the X chromosome. Inevitably, dependencies arise that have to be accounted for. This paper will in detail explore the complex statistical interpretation of X-chromosomal STR markers, focusing on likelihood calculations. Specifically, we will investigate how the phase uncertainty of haplotypes comes into play in the statistical evaluations and what curious effects this phenomenon can have. The starting point is the different real cases where the weight of evidence has provided unexpected results that require further investigation in order to be fully understood. We will touch upon subjects such as association between alleles, recombinations, and mutations. The aim of this study is to facilitate a better understanding of the interaction between the concepts in addition to provide an understanding why good estimates of haplotype frequencies are crucial. The individual subjects have been discussed in other fields, whereas this study will focus on forensic applications where few studies have been conducted relating to the understanding of how these concepts interact.

Chinese Xibe population genetic composition according to linkage groups of X-chromosomal STRs: population genetic variability and interpopulation comparisons

Background: The Xibe population is one of China’s officially recognised populations and is now distributed separately from west to east in the northern part of China. X-chromosomal short tandem repeats have a special inheritance pattern, and could be used as complements in forensic application, especially for complex or deficiency cases.Subjects and methods: This study obtained the allelic and haplotypic frequencies of 19 X-STR loci in the Xibe population from Xinjiang Uygur Autonomous Region, China, and studied the genetic differentiations between the Xibe and other populations.Results: The combined power of discrimination in females and males and mean exclusion chances in deficiency cases, normal trios and duo cases was at least 0.999 999 994. In the haplotypic study, the Xibe population showed a more similar pattern of haplotype distribution with Asian populations than populations from other continents, while allelic study also indicated a closer relationship between the Xibe and Asian populations.Conclusions: The 19 X-STR loci would be useful in forensic application in the studied population. The Xibe population showed a closer genetic relationship with Asian populations in the study, and more population data would be necessary for more detailed genetic relationship studies.

Genetic risk of Klinefelter's syndrome in assisted reproductive technology.

AimThe main cause of Klinefelter's syndrome (KS) has been believed to be XY sperm. Accordingly, in the intracytoplasmic sperm injection treatment of patients with KS, hereditary KS has been a concern. Therefore, this study attempted to estimate the risk before and after the assisted reproductive technology.MethodsFirst, in order to validate the safety of the gametes of the patients with KS, a fluorescent in situ hybridization (FISH) analysis, following an original cell identification method using 1052 testicular gametes of 30 patients, was conducted. Second, in the resultant 45 babies, cytogenetic and physical–cognitive screening data were analyzed. In addition, a first attempt was conducted to investigate the origin of the extra X chromosome in 11 patients with KS by using 12 X‐chromosome short tandem repeat (STR) analysis in order to estimate the paternal contribution to KS.ResultsNo sex chromosomally abnormal gamete was found in the FISH analysis and the babies were normal genetically, physically, and cognitively. In the STR, it was confirmed that most (7/11) of the patients with KS resulted from the fertilization of the XX oocytes, suggesting that a baby with KS that had been reported previously might not have resulted from XY sperm.ConclusionThese results indicate that the risk of assisted reproductive technology for patients with KS is not as high as previously expected.

Forensic characteristics and phylogenetic analyses of the Chinese Yi population via 19 X-chromosomal STR loci.

The demographic characteristics and genetic polymorphism data of 56 Chinese nationalities or 31 administrative divisions in Chinese mainland have repeatedly been the genetic research hotspots. While most genetic studies focused on some particular Chinese populations based on autosomal or Y-chromosomal genetic markers, the forensic characteristics and phylogenetic analyses of the seventh largest Chinese population (Yi ethnicity) on the X-chromosomal genetic markers are scarce. Here, allele frequencies and forensic statistical parameters for 19 X-chromosomal short tandem repeat loci (DXS7424-DXS101, DXS6789-DXS6809, DXS7423-DXS10134, DXS10103-HPRTB-DXS10101, DXS10159-DXS10162-DXS10164, DXS10148-DXS10135-DXS8378, and DXS7132-DXS10079-DXS10074-DXS10075) of 331 Chinese Yi individuals were obtained. All 19 X-chromosomal short tandem repeat (STR) loci in females were consistent with the Hardy-Weinberg equilibrium test. A total of 214 alleles were identified with the corresponding allele frequencies spanned from 0.0019 to 0.6106. The combined PE, PDF, and PDM were 0.9999999214, 0.9999999999999999999993, and 0.9999999999998, respectively. The high combined MECKrüger, MECKishida, MECDesmarais, and MECDesmarais Duo were achieved as 0.9999999617638, 0.9999999999971, 0.9999999999971, and 0.9999999931538, respectively. The findings suggested that the panel of 19 X-STR loci is highly polymorphic and informative in the Yi ethnic population and can be considered to be a powerful tool in forensic complex kinship identification. Population differentiation analyses among 12 populations indicated that significant differences in genetic structure were observed in between the Yi ethnicity and the Chinese Uyghur as well as Kazakh, and genetic homogeneity existed in similar ethno-origin or geographic origin populations.

Analysis of four novel X-chromosomal short tandem repeats within 71kb of the Xp22.3 region.

DNA testing using X-chromosomal short tandem repeat (X-STR) polymorphisms has been used in maternity/paternity and complex kinship cases. Analyses of repeat sequences, surveys on racial statistics, and development of practical applications for DNA testing continue to be reported. In this study, we identified four novel tetranucleotide STR loci located in the X chromosome, which is the basis of X-STR research. These four tetranucleotide STRs were located within 71kb of the chromosome Xp22.3 region. Using sequence analysis of the structure of repeat sequences, we identified simple repeat sequences of TAAA, CTTT, TATC, and GATA with rare insertions. We then calculated forensic statistical parameters using base length analysis. In the Japanese population, the polymorphism information content was 0.597-0.687, power of discrimination in females was 0.829-0.884, and power of discrimination in males was 0.635-0.729. As these tetranucleotide STRs are closely linked, we conducted haplotype analysis and detected that three loci (LC149476, LC149479, and LC149480) were in linkage disequilibrium. We demonstrated that the simultaneous analysis of these loci may be useful in complex kinship cases. Because these four loci can be detected by multiplex PCR, the detection of alleles at these loci can be rapidly and easily achieved. We conclude that the X-STR loci detected in this study may be useful tools in complex kinship cases and may increase the reliability of genetic testing.

Genetic diversity study on 12 X-STR loci of investigator® Argus X STR kit in Bangladeshi population

The X-chromosome short tandem repeat (STR) loci are of particular interest for solving complex kinship and paternity cases. Here, we report the genetic data from 209 unrelated Bangladeshi individuals (102 males and 107 females) that were genotyped using the 12 X-chromosomal STR markers included in the Investigator® Argus X-12 kit (Qiagen). The 12 X-STR markers are located in four linkage groups (linkage group I: DXS10135, DXS10148, and DXS8378; linkage group II: DXS7132, DXS10079, and DXS10074; linkage group III: DXS10103, HPRTB, and DXS10101; and linkage group IV: DXS10146, DXS10134, and DXS7423). Allelic frequencies of the 12 X-STR loci and haplotype frequencies of the four linkage groups were investigated. No significant difference was observed in the allele frequencies of males and females. Distributions of heterozygosity were observed from 64.5 to 92.5% among the studied 12 X STR loci. DXS10135 and DXS10101 loci were found to be most polymorphic. For all the four linkage groups, the haplotype diversity was found to be greater than 0.986. A total of 95, 73, 66, and 74 haplotypes were observed in linkage groups I, II, III, and IV, respectively. Hardy-Weinberg equilibrium tests showed no significant deviation from expected values for all 12 loci (p>0.05). The exact test for pairwise linkage disequilibrium for the 12 loci in the male samples did not show any significant linkage disequilibrium except the DXS10103 and DXS10101 loci after the p values were corrected by Bonferroni's correction for multiple testing (p>0.05/66). A combined power of discrimination in male and female individuals were 0.999999998159791 and 0.999999999999993, respectively. The combined mean exclusion chance were 0.999997635 in deficiency cases, 0.999999996 in normal trio cases, and 0.999999178 in duo cases. The currently investigated Bangladeshi population showed significant differences when compared with previously reported X-STR data from other 12 populations. The results of the data analysis indicated that all the loci in the Investigator® Argus X 12 kit were fairly informative and might be useful in forensic application and kinship analysis in Bangladeshi population.

Genetic diversity and haplotypic structure of Chinese Kazak ethnic group revealed by 19 STRs on the X chromosome

X-chromosomal short tandem repeats (X-STRs) have been widely used in forensic practices involving complicated ties of kinship over the past years, and also play an increasingly important role in population genetics. To study the genetic polymorphisms of 19 STR loci on X chromosome in Chinese Kazak ethnic group, we investigated the allelic and haplotypic frequencies of the 19 loci in 300 (149 males and 151 females) unrelated healthy individuals from Ili Kazak Autonomous Prefecture, Xinjiang Uigur Autonomous Region of China after having evaluated the forensic application value of these loci in forensic sciences, and then compared the population distinctions between the Kazak group and other reference groups. We observed a total of 240 alleles at these X-STR loci with the corresponding allelic frequencies ranging from 0.0017 to 0.5917. In the study, the highest polymorphism was found at DXS10135 locus. The combined power of discrimination in females was 0.999999999999999999999985 and in males 0.999999999999968. The present study indicates that the 19 X-STR loci are very useful for both forensic identification cases and kinship analyses involving a female offspring.

Population genetic data for 12 X-STR loci in the Northern Han Chinese and StatsX package as tools for population statistics on X-STR

The X-chromosomal short tandem repeat (X-STR) has the advantage in female traces identification against male contamination and in complex kinship cases. In this study, a total of 516 Northern Han Chinese were genotyped using the Investigator® Argus X-12 QS Kit and pairwise genetic distances (FST) were measured between Northern Han Chinese and 35 published populations using the same 12 X-STR loci in four presumed linkage groups (LG). Meanwhile, the StatsX package was compiled to aid the analysis of population statistics on X-STR. Off-ladder alleles were investigated by Sanger sequencing or next generation sequencing (NGS). The results showed that high combined PDM, PDF, MECKrüger, MECKishida, MECDesmarais and MECDesmarais Duo based on allele frequencies were achieved as 0.999999998, >0.999999999, 0.999996425, 0.999999993, 0.999999993 and 0.999998732, respectively, so did they based on haplotype frequencies. Averaged FST and multidimensional scaling (MDS) plot generally mirrored with the biogeography distribution of the studied populations and their historical relationships. A total of 16 unique off-ladder alleles were observed in this experiment, four of which have not been reported yet. The StatsX package could obtain full concordance with established software. Overall, the Investigator® Argus X-12 QS Kit may provide high polymorphic information for forensic identification and kinship analysis in the Northern Han Chinese population, and the StatsX package can make the workflow smoother for researchers to do population statistical analysis on X-STR.