Analysis of 8 X-chromosomal markers in the population of central Croatia

To analyze 8 X-linked short tandem repeat (STR) markers in the population of central Croatia and to evaluate their forensic efficiency.

We carried out a statistical analysis of the data from previously performed genetic analyses, collected during routine forensic work by the Forensic Science Centre ''Ivan Vučetić.'' Mentype® Argus X-8 PCR amplification kit was used for typing the data of 99 unrelated healthy women and 78 men from central Croatia. Haplotype frequencies were calculated only in male samples. Arlequin 3.5 software was used to assess Hardy-Weinberg equilibrium (HWE), linkage disequilibrium (LD), observed and expected heterozygosity. Power of discrimination (PD) for men and women, polymorphism information content (PIC), power of exclusion, and mean exclusion chance for deficiency cases, normal trios, and duos were determined using online database ChrX-STR.org.

In female samples, deviations from HWE (P=0.006) for each locus were not found. LD test performed both on female and male samples revealed no significant association between markers (P=0.002). DXS10135 was the most polymorphic locus (PIC=0.931). PD varied from 0.692 to 0.935 in male and from 0.845 to 0.992 in female samples. Combined PD reached 99.999999% in men and 99.9999999999% in women.

Performed analyses revealed that the studied marker set contained polymorphic markers with high power of discrimination. We can conclude that Mentype® Argus X-8 PCR is suitable for application in the population of central Croatia. Results of this study, together with collected allele and haplotype frequencies, are the first step in establishing a national reference X-STR database based on 8 X-STR loci.