亲权鉴定中的常染色体STR三等位基因型案例分析

Analysis of autosomal STR tri-allelic patterns in paternity testing

目的探讨STR基因座三等位基因型的分布特点及遗传机制。方法通过华夏TM白金PCR扩增试剂盒和AGCU Expressmarker 22试剂盒共同证实在亲子鉴定检案6028例(共15973人)中发现的三等位基因型,总结三等位基因型分布特点及检出频率;并通过Sanger测序验证新发现的D6S1043和D1S1656基因座的三等位基因型。结果三等位基因型检出总频率为0.5634‰(9/15973),其中D6S1043和D18S51基因座均检出2例(0.1252‰,2/15973),D1S1656、D2S441、D13S317、Penta E、Penta D基因座均检出1例(0.0626‰,1/15973)。D13S317、D18S51、Penta E、Penta D等4个STR基因座三等位基因型较常见,D2S441和D13S317基因座的三等位基因型较少见。D1S1656基因座的Ⅰ型三等位基因型和D6S1043基因座Ⅱ型三等位基因型未见报道。结论个体的嵌合情况和取样过程会导致Ⅰ型三等位基因模式中原本的基因和突变基因的比例会出现多种形式,遵循优势等位基因的峰高为另外两者之和。Ⅱ型三等位基因模式的形成可能源于非等位同源重组。在亲子鉴定和个体识别中,STR分型的准确性及对STR三等位基因型遗传特征的理解对鉴定意见的准确性至关重要。

Objective Investigation of the distribution characteristics and mechanism of inheritance of tri-allelic patterns in the STR locus.Methods Confirmed the tri-allelic patterns found in 6028 parentage test cases by the HuaxiaTM Platinum kit and AGCU Expressmarker 22 Kit,and summarized the characteristics of the distribution of the tri-allelic patterns and their detection frequencies;and confirmed the newly discovered tri-allelic patterns located in the D6S1043 locus and in the D1S1656 locus by STR typing and Sanger sequencing.Results The total frequency of the tri-allelic patterns was 0.5634‰(9/15973),of which two cases(0.1252‰,2/15973)were detected in both D6S1043 and D18S51,and one case(0.0626‰,1/15973)was detected in D1S1656,D2S441,D13S317,Penta E,and Penta D.The three allelic genotypes of the four STR loci,D13S317,D18S51,Penta E,and Penta D,are more common,while the three allelic genotypes of the D2S441 and D13S317 loci are less common.The typeⅠtriallelic genotype of D1S1656 locus and the typeⅡtriallelic genotype of D6S1043 locus have not been reported.Conclusion The individual’s chimerism and sampling process can lead to various forms of the proportion of original genes and mutated genes in the typeⅠtriallelic gene pattern,following the peak height of the dominant allele as the sum of the other two.The formation of typeⅡtriallelic gene patterns may be attributed to non allelic homologous recombination.The accuracy of STR typing and understanding of the genetic characteristics of STR triallelic genotypes are crucial for the accuracy of identification opinions in parent-child identification and individual identification.