Genetic diversity and haplotypic structure of Chinese Kazak ethnic group revealed by 19 STRs on the X chromosome.

X-chromosomal short tandem repeats (X-STRs) have been widely used in forensic practices involving complicated ties of kinship over the past years, and also play an increasingly important role in population genetics. To study the genetic polymorphisms of 19 STR loci on X chromosome in Chinese Kazak ethnic group, we investigated the allelic and haplotypic frequencies of the 19 loci in 300 (149 males and 151 females) unrelated healthy individuals from Ili Kazak Autonomous Prefecture, Xinjiang Uigur Autonomous Region of China after having evaluated the forensic application value of these loci in forensic sciences, and then compared the population distinctions between the Kazak group and other reference groups. We observed a total of 240 alleles at these X-STR loci with the corresponding allelic frequencies ranging from 0.0017 to 0.5917. In the study, the highest polymorphism was found at DXS10135 locus. The combined power of discrimination in females was 0.999999999999999999999985 and in males 0.999999999999968. The present study indicates that the 19 X-STR loci are very useful for both forensic identification cases and kinship analyses involving a female offspring.