Genetic profile characterization of 10 X-STRs in four populations of the southeastern region of Brazil

Genetic Polymorphisms and Forensic Parameters of Thirteen X-Chromosome Markers in the Iraqi Kurdish Population

X-chromosome short tandem repeat (X-STR) tools are crucial in forensic genetics and human population fields. This study presents the development and validation of a multiplex STR system consisting of thirteen X-STR loci and amelogenin specific to the human X chromosome. The system was optimized and tested for species specificity, sensitivity, stability, and DNA mixture using 9947A female and 9948 male control genomic DNA. The amplified products of nine loci were sequenced to determine the correct amplicon length. Allele frequencies, forensic parameters, mean exclusion chance (MEC), linkage disequilibrium (LD), and allelic patterns were investigated using DNA samples from 225 (159 male, 66 female) unrelated Kurdish individuals who live in Sulaymaniyah province in the Kurdistan region of Iraq. The most informative locus in the Kurdish population was GATA172D05, while the least informative locus was DXS10164. The results demonstrated that the 13 X-STR system is highly polymorphic and sensitive for forensic DNA identification. Genetic distance-based clustering, metric multidimensional scaling (MDS), and correlation matrix were analyzed for 19 ethnic groups and populations. The phylogenetic tree showed that populations clustered according to their ethnogeographic relationships. The findings revealed genetic links between the Iraqi Kurds, Caucasians, Iraqi Arabs, United States (U.S.) ethnic groups, and Chinese populations.

Genetic characterization of an X-STR decaplex system in the State of Mato Grosso, Brazil: distribution, forensic efficiency and population structure

Studies with X-STR loci show population genetic substructure, which makes necessary the characterization of such markers in the different geographical and/or ethnic populations. Therefore, this study assessed the distribution and forensic efficiency of an X-STR decaplex system in the population of the State of Mato Grosso, as well as analysed the population structure of this State based on the aforementioned system. All X-STR markers were in Hardy-Weinberg equilibrium and linkage equilibrium, and the DXS6809 was the most informative marker. The power of discrimination value in females and males was 0.99999999995 and 0.9999994, respectively. Analysis of molecular variance indicated 1.10% (p < 0.00001) of heterogeneity among Europeans, Africans, Brazilians and other Latin Americans, and in relation to such groups, the population of the State of Mato Grosso showed lower genetic variation when compared with the Brazilian group (-0.10%, p = 0.67327). The genetic distance analysis showed lower values of F _ST (0.0004 ≤ F _ST ≤ 0.00331), with non-significant p value (p > 0.00024), between the populations of Mato Grosso and Mato Grosso do Sul, Paraná and the Southeast region of Brazil (except for one sample of Rio de Janeiro). F _ST values with significant p values (p ≤ 0.00024) were obtained between the population of Mato Grosso and Iberian, African and some Latin American populations. The X-STR decaplex system proved to be extremely useful in the population of the State of Mato Grosso, and the data obtained does not show the need for a specific forensic database for this State in relation to the Brazilian populations compared in this study, except for population of Rio de Janeiro.

Exploring the applicability of analysing X chromosome STRs in Brazilian admixed population

Kinship and parentage analyses always involve one sample being compared to another sample or a few samples with a specific relationship question in mind. In most cases, the analysis of autosomal STR markers is sufficient to determine the genetic kinship. However, when genetic profiles are reconstructed from supposed relatives, for whom the family configuration available for analysis is deficient, the examination may be inconclusive. This study reports practical examples of actual cases analysing the efficiency of the chromosome X STR (STR-ChrX) markers. Three cases with different degrees of efficiency and impact were selected as follows: the identification of two charred bodies in a traffic accident, in which the family setting available was not complete, and one filiation analysis resulting from rape. This is the first paper reporting the use of the multiplex STR 12 ChrX in actual cases using the software Familias 1.8 and Brazilian regional frequency data. Our study clarifies the complex analysis using this powerful tool for professionals in the forensic science community, for both civil and criminal justice. We also discuss state-of-the-art ChrX STR markers and its implications and applications for legal procedures. The data presented here should be used in other studies of complex cases to improve the progress of the current justice system.

Genetic profile characterization of ten X-STRs in a sample from Paraná, Brazil

This work reports the allele frequencies for ten X-STRs (DXS8378, DXS7132, DXS9898, DXS6809, DXS9902, DXS6789, DXS7133, DXS7423, GATA172D05, GATA31E08) in a sample of 800 individuals from Paraná, Brazil. No deviations from the Hardy-Weinberg equilibrium were observed. Linkage disequilibrium analysis did not reveal association between the X-STRs. High overall power of discrimination was obtained for female and male samples, and high probability of exclusion was observed in father/mother/daughter trios and father/daughter duos. Genetic comparisons revealed significant differences between Paraná and other Brazilian populations.

Development of two multiplex PCR systems for the analysis of 14 X-chromosomal STR loci in a southern Brazilian population sample

We developed two multiplex systems for the coamplification of X-chromosomal short tandem repeats (STRs). X-Multiplex 1 consisted of DXS6807, DXS6800, DXS7424, DXS101, GATA172D05 and HPRTB and X-Multiplex 2 consisted of DXS8378, DXS9898, DXS6801, DXS6809, DXS6789, DXS7133, DXS8377 and DXS7423. In addition, we present allele frequencies for these loci in a south Brazilian population comprising 124 females and 141 males and haplotype frequencies of linked markers for males. Hardy-Weinberg equilibrium (HWE) was tested in the female sample and no significant deviations were found after applying Bonferroni's correction. Linkage disequilibrium (LD) tests were performed for all pairs of loci and three significant results, out of 91 pairwise comparisons, were obtained. We did not find any evidence of linkage disequilibrium between close or linked markers. The power of discrimination in females (PD(F)) varied between 0.832 for DXS6801 and 0.987 for DXS8377. DXS6801 was the least informative marker (PIC = 0.605), while DXS8377 was the most polymorphic (PIC = 0.911), followed by DXS101 (PIC = 0.872). Genetic distances were estimated for each STR marker applying the calculation of F (ST) between our total sample and other studies from Brazil, Europe, Asia and Africa. The most distant populations were Japan, Korea, China, Ghana and Uganda.

Extensive survey of 12 X-STRs reveals genetic heterogeneity among Brazilian populations

The admixed Brazilian population shows high levels of genetic variability, which resulted from the contribution of three main ethnicities, Amerindian, European, and African. However, due to its huge territory, admixing has been asymmetrical, i.e., the relative contribution from each ethnicity has been unequal in the five geopolitical regions of the country. The aim of this study was to describe genetic variability using a panel of short-tandem repeats on the X chromosome (X-STR) in order to perform a comprehensive evaluation of the usefulness of such markers for forensic purposes in Brazil. Twelve X-STR (DXS9895, DXS7132, DXS6800, DXS9898, DXS6789, DXS7133, GATA172D05, DXS7130, HPRTB, GATA31E08, DXS7423, and DXS10011) were chosen and tested in a sample of 2,234 individuals belonging to 16 out of the 27 Brazilian States, representing all of its five geopolitical regions. No markers showed significant deviation from the Hardy-Weinberg equilibrium, even when analyses were partitioned to represent geopolitical regions. Genetic diversity per locus ranged from 67% (DSX7133) to 95% (DXS10011), and the State of Ceará showed the highest average genetic diversity (79% for all 12 X-STR markers). Considering the Brazilian population as a whole, the power of discrimination of the 12 X-STR panel in females (PDF) was 0.999999999999994, while the power of discrimination in males (PDM) was 0.9999999969. Such high values suggest the potential of that panel to be used in forensic applications and relatedness tests among individuals. Comparisons among the Brazilian populations investigated revealed significant differences when they were compared among each other, a pattern that was maintained when additional populations from Europe and Latin America were compared to Brazilians. Our results highlight the need and usefulness of specific genetic database for forensic purposes in Brazilian populations.