Genetic polymorphism of 12 short tandem repeat on chromosome X loci in Shenzhen, China: a pedigree investigation / 中国组织工程研究

ABSTRACT

BACKGROUND: The special genetic law of short tandem repeat on chromosome X (X-STR) makes it incomparable with autosome markers in forensic identification. However, the population genetics data is far less than that of the autosome STR, and especially the haplotype data are rarely reported.OBJECTIVE: To study the genetic polymorphism of 12 X-STR loci in Shenzhen area by pedigree analysis, aiming to provide scientific and effective data for the application of X-STR in forensic medicine and genetics. METHODS: The blood samples of 118 families were taken to extract DNA by Chelex-100, followed by PCR amplification using Investigator Argus X-12 kit. The frequency of alleles of 231 unrelated individuals was counted by direct counting method and Excel software. Hardy-Weinberg equilibrium test was performed on 12 X-STR loci of female samples by chi-square test. Discrimination power and mean exclusion chance were calculated according to the formula. Pedigree analysis was done to identify haplotypes of female samples and the haplotype frequencies of 4 linkage groups in 111 fathers and 119 mothers were calculated using direct counting method and Excel software.RESULTS AND CONCLUSION: In this study, 349 haplotypes were obtained. There were 238, 139, 153 and 157 haplotypes in linkage groups X1-X4, respectively. The polymorphism of DXS10135 locus was the highest with 21 alleles,while the polymorphism of DXS7423 locus was the worst with only 4 alleles. The combined discrimination power was 0.99999999 in males and 0.99999999 in females. The combined mean exclusion chance was 0.99999999 in trio cases,and 0.99999811 in duo cases. These findings indicate that the X-12 detection system has high polymorphism in Shenzhen Han population, and has important application value in forensic individual identification and paternity testing.