Abstract

In this study, we aimed to demonstrate the importance and utility of polymorphic short tandem repeat (STR) found on the human X chromosome and to provide the first allelic frequency data of X-STR (X chromosomal) loci in the Turkish population. Blood samples were taken from unrelated individuals (135 males and 129 females) from different regions of the country. Primers were designed according to gene bank data (www.gdb.org) and synthesised by the Köln Blutgruppen Institute. The primers amplified the following loci on the X chromosome: DXS8377, DXS101, DXS6789, STRX-1 and HUMHPRTB. Our data showed that two loci, DXS8377 and DX101, had the highest number of alleles (18) and the polymorphism information content (PIC) values of these loci were 0.9 and 0.87, respectively and were higher than those of other loci. In the other loci examined, 11 (STRX1), 10 (DXS6789) and 9 (HPRTB) alleles were detected and the PIC values of these loci were 0.78, 0.68 and 0.70, respectively. The highest (0.899) and lowest (0.674) rate of heterozygosity was found in the DXS8377 and HPRTB loci, respectively. In all loci, the power of discrimination for female (PD^F) values were higher than the power of discrimination for male (PD^M) values. The locus with the highest PD^F value was DXS8377 (0.9841). The mean exclusion change (MEC) value of this locus also proved to be the highest for both father-mother-child and father-child. The locus with the lowest MEC value was DXS6789. To use calculations of probabilities of genetic results for forensic purposes, allelic frequencies in individuals in the community should be determined. Our study provides the first data from the Turkish population.

Key words: X chromosomal (X-STR), forensic genetics, forensic sciences, DNA, kinship testing, paternity.

Abbreviation

Abbreviations: STR, Short tandem repeat; PCR, polymerase chain reaction; PIC,polymorphism information content; PD^F, power of discrimination for females; PD^M,power of discrimination for males; MEC, mean exclusion chance.