X chromosome STR markers are a useful tool in population genetics, they provide supplementary information for forensic and kinship analysis where autosomal and Y chromosome information is not enough. A total of 100 unrelated individuals from Imbabura-Ecuador were genotyped using the X-STR Decaplex system (DXS8378, DXS9902, DXS7132, DXS9898, DXS6809, DXS6789, DXS7133, GATA172D05, GATA31E08, and DXS7423). Allele frequencies and population parameters were calculated for each STR. The most informative marker was DXS6809 and the least informative was DXS7133. High discrimination power values were obtained (greater than 99.99%), as well as high mean exclusion chance in trios (mother / daughter / father) 0.9999948011 and duos (father/daughter) 0.9992880836. The genetic distance (F ST ) obtained comparing the Ecuadorian population and the Pichincha province population show low genetic distances. The data analyzed confirmed the potential of these 10 X-STRs.

The X-STR markers represent a powerful tool to complement the information provided by the autosomal and Y chromosome markers, particularly, in cases involving at least one woman. In the present study, allele frequencies, power of exclusion (PE), power of discrimination (PD) and polymorphism information content (PIC) were analyzed for 12 X chromosome loci. A total of 200 unrelated Ecuadorian individuals were selected for the population analysis. The data showed that DXS10135 locus had the highest power of discrimination value (PD = 0.9351), and polymorphism information content (PIC = 0.9313). The heterozygosity observed ranged from 0.9300 to 0.6400. The power of exclusion varied between 0.3417 to 0.8570 for DXS10135 and DXS8378 respectively. No significant departure from Hardy Weinberg equilibrium (HWE) was detected for any of the analyzed markers. The X-STR markers have demonstrated their potential to efficiently complement the analysis to solve complex kinship and forensic cases.

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