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In an attempt to increase the discrimination capacity (DC) and reduce the adventitious match probability, a 6-dye multiplex Y-chromosomal short tandem repeat (Y-STR) panel named Y34plex was constructed that combined 25 Y-chromosomal markers (DYS456, DYS627, DYS390, DYS570, DYS635, DYS385a/b, DYS448, DYS437, DYS533, DYS449, DYS481, DYS392, DYS391, DYS389I, DYS460, YGATAH4, DYS438, DYS389II, DYS19, DYS458, DYF387S1a/b, DYS439, DYS393, DYS576, and DYS518) in widely used commercial kits, with nine highly polymorphic Y-STR loci (DYS557, DYS527a/b, DYS593, DYS444, DYS596, DYS643, DYS447, DYS549, and DYS645). The Y34plex is a promising type system to distinguish both unrelated and related male individuals due to the incorporation of rapidly mutated Y-STR loci. A validation study of the Y34plex was performed and followed the guidelines of the Scientific Working Group on DNA analysis methods. Results show that full Y-STR profiles were obtained from male/female DNA mixtures with 125 pg of male DNA in the presence of 50 ng of female DNA. The ability to tolerate polymerase chain reaction inhibitors commonly contained in forensic casework samples demonstrated the applicability and robustness of the Y34plex. Compared with the Yfiler Plus kit, the novel panel showed an increased power of discrimination in Chinese Wuxi Han population (n = 434). The overall haplotype diversity of the Y34plex was 0.999606, whereas DC value was 0.956221, which is suitable for use on forensic paternal investigation.

As a result of the expansion of old Tibet on the Qinghai-Tibet Plateau, Tibetans diverged into three main branches, Ü-Tsang, Amdo, and Kham Tibetan. Ü-Tsang Tibetans are geographically distributed across the wide central and western portions of the Qinghai-Tibet Plateau while Lhasa is the central gathering place for Tibetan culture. The AGCU Y30, a 6-dye fluorescence kit including 30 slowly and moderately mutated Y-STR loci, has been validated for its stability and sensitivity in different biomaterials and diverse Chinese populations (Han and other minorities), and widely used in the practical work of forensic science. However, the 30 Y-STR profiling of Tibetan, especially for Ü-Tsang Tibetan, were insufficient. We utilized the AGCU Y30 to genotype 577 Ü-Tsang Tibetan unrelated males from Lhasa in the Tibet Autonomous Region of China to fill up the full and accurate Y-STR profiles. A total of 552 haplotypes were observed, 536 (97.10%) of which were unique. One hundred and ninety-four alleles were observed at 26 single copy loci and the allelic frequencies ranged from 0.0017 to 0.8180. For the two multi-copy loci DYS385a/b and DYS527a/b, 64 and 36 allelic combinations were observed, respectively. The gene diversity (GD) values ranged from 0.3079 at DYS391 to 0.9142 at DYS385a/b and the overall haplotype diversity (HD) was 0.9998, and its discrimination capacity (DC) was 0.9567. The population genetic analyses demonstrated that Lhasa Ü-Tsang Tibetan had close relationships with other Tibetan populations from Tibet and Qinghai, especially with Ü-Tsang Tibetan. From the perspective of Y haplogroups, the admixture of the southward Qiang people with dominant haplogroup O-M122 and the northward migrations of the initial settlers of East Asia with haplogroup D-M175 hinted the Sino-Tibetan homologous, thus, we could not ignore the gene flows with other Sino-Tibetan populations, especially for Han Chinese, to characterize the forensic genetic landscape of Tibetan.

Predicting the biogeographical ancestries of populations and unknown individuals based on ancestry-informative markers (AIMs) has been widely applied in providing DNA clues to criminal investigations, correcting the factor of population stratification in genome-wide association studies (GWAS), and working as the basis of predicting the externally visible characteristics (EVCs) of individuals. The present study chose Chinese Xinjiang Kazak (XJK) group as research object using a 165 AIM-SNPs panel via next generation sequencing (NGS) technology to reveal its ancestral information and genetic background by referencing the populations’ data from 1000 Genomes Phase 3. After the Bonferroni correction, there were no significant deviations at the 165 AIM-SNP loci except two loci with homozygote in the studied XJK group. Ancestry information inference and populations genetic analyses were conducted basing on multiplex statistical methods such as forensic statistical parameter analyses, estimation of the success ratios with cross-validation, population tree, principal component analysis (PCA), and genetic structure analysis. The present results revealed that XJK group had the admixed ancestral components of East Asian and European populations with the ratio of about 62:37.

The male-specific region of the human Y chromosome is a useful genetic marker for genealogical searching, male inheritance testing, and male DNA mixture deconvolution in forensic studies. However, the Y chromosomal short tandem repeats (Y-STRs) are difficult to distinguish among related males due to their low/medium mutation rate. In contrast, rapidly mutating (RM) Y-STRs exhibit unusually high mutation rates and possess great potential for differentiating male lineages. In this study, we developed a novel Y-STRs multiplex amplification assay of 32 RM Y-STRs by fragment analysis using six dye-labeled technologies (FAM, HEX, TAMRA, ROX, VIG, and SIZ). The development and the validation of the kit were carried out in accordance with the Scientific Working Group guidelines on DNA Analysis Methods. Identical allelic profiles of the 32 RM Y-STRs using a DNA 9948 sample as the positive control could be observed at different concentrations of PCR reagents. Further, the RM Y-STRs did not show cross-reactions with other common animal species, and the developed assay could tolerate interferences from common PCR inhibitors and mixed DNA samples. More importantly, the kit showed relatively high sensitivity and could detect trace DNA samples. Genetic distributions of 32 RM Y-STRs in the Guizhou Han population revealed that these RM Y-STRs showed relatively high genetic diversities. In conclusion, the RM Y-STR assay developed here showed good species specificity, high sensitivity, tolerance to inhibitors, and sample compatibility, which can be viewed as a highly efficient tool with high discrimination capacity for forensic male differentiation.

A number of artifacts produced in forensic DNA typing make the interpretation more complicated and even lead to typing errors. Here, we reported the cause of false-tetra-allelic patterns of STR locus D10S1435 at the sequence level. To confirm the true genotyping, the sample with four allelic peaks was re-amplified and sequenced. The amplicon sequences of D10S1435, D20S482, D6S1017, and D10S1248 loci were analyzed by software BioXM and RNAstructure. We successfully reproduced the four-peak phenomenon by adding various concentration of magnesium chloride into the loading mixtures to simulate the suboptimal electrophoresis conditions. The false four allelic peaks may be caused by the specific nucleotide sequence of locus D10S1435 which tends to form secondary structures under the suboptimal electrophoresis conditions. The relatively high GC content and extremely uneven distribution give the amplicon a potency to resist complete denaturation at the phase of sample preparation and a tendency to form intra- and intermolecular secondary structures during post-injection.

The Y chromosome short tandem repeat (Y-STR) haplotyping method has been widely used in forensic applications. However, the existing Y-STR panels are not the ideal tools for criminal investigation and database applications because of their relatively low discriminatory capacity (DC) or high mutation rates. In the present study, the multiplex PCR assay (AGCU Y30) for simultaneous amplification of 30 slowly and moderately mutated Y-STR loci labeled by 6-dye fluorescence was developed and validated. The AGCU Y30 assay was capable of amplification purified DNA from casework and database samples on FTA™ cards in direct amplification module with a 10 μL reaction volume. Furthermore, the genetic diversities and forensic parameters of AGCU Y30 were performed using 719 unrelated male samples, demonstrating its high level of genetic polymorphisms and DC in Nantong Han population. This validation study demonstrated good sensitivity, mixture samples, inhibitor tolerance, precision, and concordance for the AGCU Y30, which is suitable for forensic investigation and database construction.

Background Y‐chromosomal genetic marker haplotypes of individuals can define the paternal kinship or genealogies to which they belong and further provide clues for forensic individual identifications. Studying the genetic structure of the Mongolian group will help to bring to light the Mongolian ethnic origin, and explicate the genetic affinities among the studied and compared populations. Some forensic scientists have studied the genetic background of the Mongolian group based on different molecular genetic markers. These studies were of very great reference significance for the Mongolian group genetic research, whereas the investigation of Y‐STR haplotype data in the Xinjiang Mongolian group is still insufficient. Methods Genetic characteristics of 182 unrelated healthy male Mongolian individuals were revealed by 41 Y‐chromosomal short tandem repeat and 3 insertion/deletion molecular genetic markers. Furthermore, analyses of molecular variance programs, multi‐dimensional scaling plots, and phylogenetic tree reconstructions were operated to explore the genetic relationships of the Xinjiang Mongolian group with comparative 23 populations from China and 33 populations from worldwide nations. Results The genetic diversity values ranged from 0.0641 (rs771783753) to 0.9502 (DYF387S1). A total of 165 distinct haplotypes were identified, of which 150 (90.91%) were unique. The discrimination capacity, match probability, and haplotype diversity of 44 loci were 0.9066, 0.0067, and 0.9988, respectively. Additionally, the Mongolian group had the most intimate relationship with Gansu Dongxiang (R ST = 0.0165), followed by HulunBuir Mongolian (R ST = 0.0187), Inner Mongolia Daur (R ST = 0.0202) as well as other three minority ethnic groups from the Xinjiang region (R ST, Investigating genetic characteristics of the Mongolian group using 41 Y‐chromosomal short tandem repeat and 3 insertion/deletion molecular genetic markers. Exploring the genetic relationships between the Mongolian group and 23 comparison populations from China, as well as between the Mongolian group and 33 comparison populations from worldwide nations.

In recent years, insertion/deletion (InDel) markers have become a promising and useful supporting tool in forensic identification cases and biogeographic research field. In this study, 30 InDel loci were explored to reveal the genetic diversities and genetic relationships between Chinese Xinjiang Hui group and the 25 previously reported populations using various biostatistics methods such as forensic statistical parameter analysis, phylogenetic reconstruction, multi-dimensional scaling, principal component analysis, and STRUCTURE analysis. No deviations from Hardy-Weinberg equilibrium tests were found at all 30 loci in the Chinese Xinjiang Hui group. The observed heterozygosity and expected heterozygosity ranged from 0.1971 (HLD118) to 0.5092 (HLD92), 0.2222 (HLD118) to 0.5000 (HLD6), respectively. The cumulative probability of exclusion and combined power of discrimination were 0.988849 and 0.99999999999378, respectively, which indicated that these 30 loci could be qualified for personal identification and used as complementary genetic markers for paternity tests in forensic cases. The results of present research based on the different methods of population genetic analysis revealed that the Chinese Xinjiang Hui group had close relationships with most Chinese groups, especially Han populations. In spite of this, for a better understanding of genetic background of the Chinese Xinjiang Hui group, more molecular genetic markers such as ancestry informative markers, single nucleotide polymorphisms (SNPs), and copy number variations will be conducted in future studies.

In the present study, we calculated the allelic frequencies and forensic descriptive parameters of Hui ethnic minority on the basis of 21 short tandem repeat (STR) loci aiming at understanding population structure better and enriching population genetic database. Bloodstain samples of 506 unrelated healthy Hui individuals in Xinjiang Uygur Autonomous Region were collected. Altogether 268 alleles were observed and the allelic frequencies ranged from 0.0010 to 0.5306. The combined power of discrimination and the cumulative probability of exclusion of the 21 STR loci in Hui ethnic minority were 0.9999999999999999999999998697 and 0.9999999968, respectively. Population data obtained manifested that the panel of 21 STR loci could provide robust genetic information for individual identification and paternity testing involved in forensic applications for Huis of Xinjiang Region. Furthermore, the present results of interpopulation differentiations, phylogenetic trees and principal component analysis which were conducted based on the overlapping 16 STR loci revealed that Hui group was genetically close to Xibe ethnic group and Han populations from different regions.

Predicting the biogeographical ancestries of populations and unknown individuals based on ancestry-informative markers (AIMs) has been widely applied in providing DNA clues to criminal investigations, correcting the factor of population stratification in genome-wide association studies (GWAS), and working as the basis of predicting the externally visible characteristics (EVCs) of individuals. The present study chose Chinese Xinjiang Kazak (XJK) group as research object using a 165 AIM-SNPs panel via next generation sequencing (NGS) technology to reveal its ancestral information and genetic background by referencing the populations' data from 1000 Genomes Phase 3. After the Bonferroni correction, there were no significant deviations at the 165 AIM-SNP loci except two loci with homozygote in the studied XJK group. Ancestry information inference and populations genetic analyses were conducted basing on multiplex statistical methods such as forensic statistical parameter analyses, estimation of the success ratios with cross-validation, population tree, principal component analysis (PCA), and genetic structure analysis. The present results revealed that XJK group had the admixed ancestral components of East Asian and European populations with the ratio of about 62:37.

To investigate the genetic polymorphism of Y chromosome short tandem repeat (Y-STR) loci in Dong, Miao, Tujia, and Yao minority populations from Hunan Province, China. Fifty Y-STRs (DYS392, DYS389I/II, DYS447, DYS438, DYS527, DYS645, DYS596, DYS391, DYS456, DYS19, DYS593, DYS448, DYS627, DYS557, DYS437, DYS481, DYS533, DYS390, DYS385, DYF387S1, DYS460, DYS393, Y_GATA_H4, DYS439, DYS635, DYS444, DYS643, DYS549, DYS576, DYS570, DYS458, DYS449, DYS518, DYS531, DYS630, DYS622, DYS552, DYS510, DYS459a/b, DYS446, DYS443, DYS587, Y_GATA_A10, DYS520, DYS522) were analyzed for 2553 unrelated healthy male individuals from Hunan (643 Dong males, 666 Miao males, 633 Tujia males, 611 Yao males) using AGCU Y37 and AGCU Y SUPP STR amplification system. There were 624 different haplotypes in 643 unrelated Dong males, 662 in 666 unrelated Miao males, 627 in 633 unrelated Tujia males, and 587 in 611 unrelated Yao males. The haplotype diversities of Dong, Miao, Tujia, and Yao were determined as 0.999879, 0.999982, 0.999970, and 0.999860, respectively. Analysis of molecular variance (AMOVA) tests demonstrated that genetic distance between Miao and Tujia was the smallest (0.0003), while the genetic distance between Dong and Yao was the largest (0.0252). The 50 Y-STR loci in the four minority populations from Hunan Province revealed a highly polymorphic genetic distribution, which showed a high potential for population genetics and forensic practice.

Aim To determine allele frequencies and forensic statistics of 22 autosomal short tandem repeat loci in Chinese Mongolian population. Methods Blood specimens were collected from 134 unrelated healthy Mongolian individuals, and 22 short tandem repeat loci were co-amplified and genotyped. Allele frequencies and forensic parameters were calculated, and population genetic differences were analyzed among Mongolian population and other eight Chinese populations: Northern Han, Guangdong Han, Chengdu Han, Xinjiang Hui, Xinjiang Uygur, Hainan Li, Qinghai Tibetan, and Hainan Han. Results All the loci were in the Hardy-Weinberg equilibrium, and after Bonferroni correction there was no linkage disequilibrium between them. The allele frequencies of these 22 loci were between 0.0037 and 0.3657. This panel had high discriminating power and genetic polymorphism in the Mongolian population, with combined power of discrimination of 0.999999999999999999999999998399 and combined probability of exclusion of 0.9999999999566925. Structure analysis showed no evidence that these nine Chinese populations had different component distribution. However, genetic distance analysis showed significant differences among them (P < 0.05). Conclusion The combined application of these 22 loci could be useful for forensic purposes in the Mongolian population. Mongolian population had smaller genetic distances from the populations in northern China (Northern Han, Xinjiang Uygur, and Xinjiang Hui) than from the populations in Hainan province (Hainan Han and Hainan Li populations).

To investigate the genetic polymorphisms of 59 Y-chromosomal short tandem repeat (Y-STR) loci in the Yulin Han population, 229 unrelated healthy male individuals were analyzed using AGCU Y37 kit and AGCU Y-SUPP Plus kit. A total of 227 different haplotypes were obtained at the 59 Y-STR loci. Among them, 225 haplotypes were unique and 2 haplotypes occurred twice. The overall haplotypic diversity and discrimination capacity were 0.9999 and 0.9913, respectively. The phylogenetic relationships between the studied Yulin Han population and 17 previously reported reference populations were evaluated via multidimensional scaling and Neighbor-Joining analyses based on the haplotypic frequencies of 'YHRD Maximal Loci'. Phylogenetic analysis revealed that Yulin Han population was closely related to Chinese Han and Hunan Yao populations. These results demonstrated that the 59 Y-STR loci were useful for forensic applications and population genetic studies.

To further illustrate the mutation traits of 21 autosomal STR loci involved in the newly developed AGCU 21 + 1 kit, randomly selected 485 trios were focused on. We have previously confirmed the biological father-mother-child relationships of these trios. Then matters of mutation rates, steps, and origins of the 21 STR loci were statically analyzed. Results showed 35 mutation events occurred at 16 STR loci of the panel during 20,370 meiosis, and the locus-specific mutation rates ranged from 0.000 to 1.134% (D3S4529), with an overall mutation rate of 1.72 × 10-3 (95%CI, 1.20-2.39 × 10-3). Mutation origins exhibited slight discrepancy between male and female germlines, 18 of the 35 mutation events were verified to be contributed by fathers and 13 by mothers, with origins of the remaining 4 events hardly to be assigned. Furthermore, 77.14% of the mutations were one-step mutation. Currently, portraits on mutability of the STR loci involved in the AGCU 21 + 1 panel were barely reported. In view of this, we conclude our data will enrich the mutation information of the 21 STR loci and provide valuable suggestions in calculating likelihood ratios for mutation-involved parental testing cases.

In recent years, insertion/deletion (InDel) markers became a promising and useful supporting tool in forensic identification cases and biogeographic research field. In this study, 30 InDel loci were explored to reveal the genetic diversities and genetic relationships between Chinese Xinjiang Hui group and the 24 previously studied populations using varies methods such as forensic statistical parameter analysis, phylogenetic reconstruction, STRUCTURE analysis, multi-dimensional scaling, and principal component analysis. The observed heterozygosity and expected heterozygosity ranged from 0.1971 (HLD118) to 0.5092 (HLD 92), 0.2222 (HLD 114) to 0.5000 (HLD 6), respectively. Besides, after Bonferroni correction, no deviations from Hardy-Weinberg equilibrium tests were found at all 30 loci in Xinjiang Hui group. The cumulative probability of exclusion and combined discrimination power were 0.988849 and 0.99999999999378, respectively, which indicated that the 30 loci could be used as complementary genetic markers for paternity test and be qualified for personal identification in forensic cases. In this study, we found that Xinjiang Hui group had close relationships with most Chinese groups, especially Han populations, and all the results based on different genetic methods we used had a strong support for this finding. The 30 InDel loci has important significance in forensic identification research, in spite of this, for a better understanding of genetic background of the Chinese Xinjiang Hui group, molecular genetic genotyping at various genetic markers is necessary in future studies.Summary StatementWe report here, a promising Individual identification and population differentiation maker which could be used in forensic cases.