Genetic analysis of 12 X-short tandem repeats loci in Serbian population

Abstract

Analysis of autosomal short tandem repeats (STRs) loci is a standard tool in forensic genetics, since it has identification capacity. However, in cases where autosomal STRs are not informative, when complex kinship or paternity cases should be solved, X-STRs could be used. Here we present forensic genetic properties of 12 X-STRs belonging to four different linkage groups (LG) using the Investigator Argus X-12 Kit. In order to assess the forensic efficiency of these markers in Serbian population, we analyzed 138 unrelated male samples. We aimed to examine allelic frequencies of the 12 X-STR loci and haplotype frequencies of the four linkage groups, as well as some forensic parameters. DNA extracted from buccal swabs was PCR amplified and analyzed by capillary electrophoresis. Statistical analysis and haplotype frequencies for LGs were performed using Arlequin 3.5 software and on-line tool available at ChrX-STR.org. The number of alleles in the loci was found to vary between 4 (DXS8378) and 20 (DXS10135 and DXS10146). Regardless to the same number of alleles, the marker DXS10135 was more informtive (PIC 0.907403) compared to DXS10146 (PIC 0.873742). Marker DXS8378 with 4 alleles was not the least informative (PIC 0.702861), but it was a marker DXS7423 (PIC 0.594342). Distributions of heterozygosity were observed from 67.4 to 91.3% among the studied 12 X STR loci, while the power of discrimination ranged from 82.2 to 98.6% in females (PDf) and from 64.9 to 91.3% in males (PDm). Power of exclusion (PE) for analyzed loci ranged from 35.4 to 82.3%. Number of detected haplotypes ranged from 83 (LG3) to 113 (LG1), with 291 unique haplotypes among four LGs. The most common haplotypes were from LG3 and LG4, both with frequency of 4.3%. We detected linkage disequilibrium within one (LG3) out of the four designated linkage groups. The results of this study could be used for further population studies and interpretation of forensic casework results.