Impact of a chromosome X STR Decaplex in deficiency paternity cases

Classical and Non-Classical HLA Alleles as Supplementary Markers in Indirect Kinship Parentage Testing

A civil paternity investigation involving the parents of the deceased alleged father in order to establish a family relationship is presented. On the basis of the 23 autosomal short tandem repeat (aSTR) genotyping results, conclusive proof of paternity was not achieved, as the probability of paternity (W) was calculated to 0.99988. Additional genetic data of 17 classical and non-classical human leukocyte alleles (HLA) typing by next-generation sequencing (NGS) at a high-resolution level supported the hypothesis of grandpaternity over the hypothesis of coincidental paternal obligate allele (POA) sharing (total WaSTR&HLA = 0.9999998). The present study demonstrates the utility of 17 HLA genetic markers-typing in the solution of deficiency cases of disputed parentage.

Genetic analysis of X-chromosomal short tandem repeat (X-STR) frequencies in Arab Iraqi male population

BACKGROUND

The X-chromosome short tandem repeat (STR) polymorphisms are a particular tool in the fields of human population genetics and personal identification. It was necessary in investigating complex kinship or deficiency cases in conditions where information on mitochondrial DNA (mtDNA) or Y chromosome polymorphisms have been used to explore their direct paternal line. This study aimed to investigate the allele frequency of (12X-STR) of 200 unrelated males from different region of Baghdad City to serve as a reference data base for individual identification in Iraqi population.

RESULTS

Twelve X-STR loci (DXS7424, HPRTB, DXS8377, GATA31E08, DXS7423, DXS8378, DXS9895, DXS10074, DXS6809, DXS7133, DXS101, DXS6807) were successfully amplified by multiplex PCR and divided into four groups. According to measures of allele frequency, the higher alleles frequency were 16, 11, 46, 11, 14, 10, 15, 15.2, 35, 11, 25, and 11 while the lowest alleles frequency were 11, 9, 52,53, 7, 17, 14, 13, 12.2,17, 36, 15, 16, 22, 29, and 17 that observed at the 12 loci respectively. Forensic efficiency parameter for DXS8377 locus in the first group showed highest polymorphic allele in the Iraqi Arab population with the frequencies ranging from 0.005 to 0.16%. The power of discrimination (PD) value ranged from 0.663 for DXS7423 locus and 0.9066 for DXS8377 locus. In addition, the polymorphism information content (PIC) value ranged from 0.602974 for DXS7423 locus to 0.899206 for DXS8377 locus.

CONCLUSIONS

Overall the X-STR markers become used as an important source of information beside the autosomal and Y-STR markers, especially for kinship testing and haplotype analysis.

Development and validation of a multiplex 19 X-chromosomal short tandem repeats typing system for forensic purposes

X-chromosome short tandem repeat (X-STR) markers are a powerful complementary system used for paternity and forensic casework. This study presents the development and validation of a new highly efficient multiplex-fluorescent-labeled 19 X-STR typing system, including DXS10079, DXS101, DXS10135, DXS10162, DXS6795, DXS6800, DXS6803, DXS6807, DXS6809, DXS6810, DXS7133, DXS7423, DXS981, DXS9902, DXS9907, GATA165B12, GATA172D05, GATA31E08 and HPRTB along with sex-typing locus, amelogenin. The system was validated according to guidelines issued by the Scientific Working Group on DNA Analysis Methods. Allele frequency and forensic parameters were investigated from 1085 (494 males and 591 females) unrelated Beijing Han individuals, the combined power of discrimination by the 19 X-STR loci in females and males, as well as the combined mean exclusion chance in trios and duos, were 0.999999999999999995, 0.99999999995, 0.9999999995, and 0.9999996, respectively. The results demonstrate that this multiplex system is robust and reliable, and considered to be a powerful tool for forensic application.

Forensic Genetics and Genotyping

Forensic genetics represents a combination of molecular and population genetics. Personal identification and kinship analysis (e.g. paternity testing) are the two main subjects of forensic DNA analysis. Biological specimens from which DNA is isolated are blood, semen, saliva, tissues, bones, teeth, hairs. Genotyping has become a basis in the characterization of forensic biological evidence. It is performed using a variety of genetic markers, which are divided into two large groups: bi-allelic (single-nucleotide polymorphisms, SNP) and multi-allelic polymorphisms (variable number of tandem repeats, VNTR and short tandem repeats, STR). This review describes the purpose of genetic markers in forensic investigation and their limitations. The STR loci are currently the most informative genetic markers for identity testing, but in cases without a suspect SNP can predict offender’s ancestry and phenotype traits such as skin, eyes and hair color. Nowadays, many countries worldwide have established forensic DNA databases based on autosomal short tandem repeats and other markers. In order for DNA profile database to be useful at a national or international level, it is essential to standardize genetic markers used in laboratories.

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.