Development Of9X-STR Loci Typing System And Genetic Analysis In Three Nationality Populations From China

Background Nowadays, autosomal and Y-chromosomal short tandem repeat (STR) markers are widely applied to forensic individual identification and paternity testing. However, in some special cases, such as the alleged father cannot be typed but the relatives of the alleged father can be investigated, identified whether presumptive half-sister have the same father but the mother cannot be tested, or paternal grandmother and granddaughter, the investigation of X-Chromosomal markers may be more informative than the investigation of autosomal polymorphisms. In recent years, there are a few commercial X-STR typing kits available, such as Investigator Argus X-12and Mentype(?) Argus X-8. However, some of the loci in these commercial kits are not suitable for Chinese population, and further these kits are expensive. This limits its application in China. To generalize the application of X-STR in forensics and to gain more information from a sample, it is necessary to develop multiplex PCR systems including a large number of loci with high polymorphism.Obejective To establish a9-locus X-STR fluorescent-multiplex PCR for forensic purposes, and to investigate the genetic polymorphism of these loci in Chinese Han, Yi and Zhuang populations in order to assess its application value in forensic science.Methods Nine highly polymorphic X-STR loci, GATA172D05, DXS10159, DXS6797, HPRTB, DXS10079, DXS6789, DXS9895, DXS10146and GATA31E08, were selected, and a9-locus fluorescent-multiplex PCR system was developed through redesigning primers, labeling fluorescence dye, and optimizing experiment conditions. Then,300,180and176unrelated individuals from Wuhan Han population, Yunnan Yi and Zhuang populations respectively were genotyped using the established multiplex PCR system, and their polymorphic parameters were calculated in order to assess their forensic application value.Results (1) A9-locus X-STR fluorescent-multiplex PCR system was established successfully. This system was robust, and compared with the single-locus genotyping results, it was consistent with the corresponding results from the established tying system.(2) All of9X-STR loci were highly polymorphic in Wuhan Han population, Yunnan Yi and Zhuang populations (PIC>0.65). The powers of discrimination in females and males of these loci were0.8650-0.9671and0.6856-0.8721respectively, and power of exclusion for parentage testing of a girl for trios and duos were0.6594-0.8497and0.5157-0.7507respectively.(3) Significant difference was observed in the distributions of allele frequencies among these three populations for these loci.Conclusion (1) The9X-STR loci selected by this study are highly polymorphic in Wuhan Han, Yunnan Yi and Zhuang populations, and are of high value in forensic application;(2) The results of population genetics investigation on these loci in Wuhan Han, Yunnan Yi and Zhuang populations provide the basic data for their forensic applications;(3) The9-locus X-STR fluorescent-multiplex PCR developed by this study is of high stability, repeatability and sensitivity, and is suitable for kinship testing in complicated cases.