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.

Back ground: X-chromosomal short tandem repeats (X-STRs) have assured to be informative and particular role in complex relationship testing. DXS6807 known as tetra nucleotides polymorphism representing eight alleles of 251-275 bp in length. DXS6807 is located in, at XP 22.2, at a genetic distance of more than 87 and 151 Cm of X-chromosome. DXS101 is located104.9–121 cM from the Xp-telomere (Xp-tel) corresponding to cytogenetic position in Xq21.33–Xq22.3.  Objective: The aim of this present study   investigates the allele frequency of two markers DXS101, DXS6807 and forensic efficiency parameters for sample of Arabic Iraqi males. Material and methods: The population of this study includes 200 males apparently healthy unrelated participants from different region of Baghdad city, their ages ranged between (20-50) years. The Genomic DNA extracted and purified successfully from blood samples.  Results: The forensic efficiency parameters result for these markers were following: polymorphism information content (PIC) of 0.834708, power of discrimination (PD) in male 0.851750, Power of exclusion (PE) 0.698316, MEC Krüger0.511679, MEC Kishida 0.694890. The forensic efficiency parameters analyzing from Arabic population were Power of discrimination (PD) = 0.73405, Polymorphism information content (PIC) =0.69489, Power of exclusion (PE) =0.482879.MEC Krüger =0.511679, MEC Kishida = 0.694890. Conclusions: The information provided establish this X-linked microsatellite marker as a valuable strategy for forensic application. DXS101is and DXS6807 recently consider more stable and suitable forensic markers for forensic application.

X-chromosomal short tandem repeats (X-STRs) have proven to be informative and particular role in complex relationship testing. In this present study demonstrates and investigate the allele frequency and forensic efficiency parameters for 200 healthy unrelated Arabic, Iraqi males for the microsatellite marker DXS10074 this marker located within a 280-kb region at Xq12 and provide stable allele useful for forensic application.