Abstract
A new 19 X- short tandem repeat (STR) multiplex PCR system has recently been developed, though its applicability in forensic studies has not been thoroughly assessed. In this study, 932 unrelated individuals from four Chinese ethnic groups (Han, Tibet, Uighur and Hui) were successfully genotyped using this new multiplex PCR system. Our results showed significant linkage disequilibrium between markers DXS10103 and DXS10101 in all four ethnic groups; markers DXS10159 and DXS10162, DXS6809 and DXS6789, and HPRTB and DXS10101 in Tibetan populations; and markers DXS10074 and DXS10075 in Uighur populations. The combined powers of discrimination in males and females were calculated according to haplotype frequencies from allele distributions rather than haplotype counts in the relevant population and were high in four ethnic groups. The cumulative powers of discrimination of the tested X-STR loci were 1.000000000000000 and 0.999999999997940 in females and males, respectively. All 19 X-STR loci are highly polymorphic. The highest Reynolds genetic distances were observed for the Tibet-Uighur pairwise comparisons. This study represents an extensive report on X-STR marker variation in minor Chinese populations and a comprehensive analysis of the diversity of these 19 X STR markers in four Chinese ethnic groups.
Highlights
Autosomal short tandem repeat (STR) markers are well-established and highly effective tools widely used for genetic identity and relationship testing[1]
In our unpublished data obtained from Southern Han family samples, the analyzed 19 X-STR loci multiplex system included seven clusters of closely linked markers: DXS10148-DXS10135-DXS8378, DXS10159-DXS10162-DXS10164, DXS 7132-DXS10079-DXS10074-DXS10075, DXS6809-DXS6789, DXS7424-DXS101, DXS10103-HPRTB-DXS10101 and DXS10134-DXS7423 which increasing the power of discrimination for joint consideration of many X STRs at a time
Hardy-Weinberg equilibrium (HWE) tests were performed on female samples
Summary
Autosomal STR markers are well-established and highly effective tools widely used for genetic identity and relationship testing[1]. X chromosome STRs, a complementary tool to autosomal STR and mitochondrial DNA (mtDNA) markers, can be used in forensic investigations such as complex kinship analysis[2]. LDE can be assessed from allele and haplotype frequencies and alleles of closely linked X chromosomal loci can be evaluated as a haplotype rather than single STRs. grouping markers into haplotypes may lead to partially redundant information (corresponding to reduce the markers used in multiplex system) when performing kinship testing[7]. It is necessary to investigate the LDE of the 19 above-mentioned markers and to calculate the efficacy of these loci through single locus and haplotype frequency analyses to assess their potential use in forensic practices
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