在亲子鉴定中,当孩子和父母之间的等位基因有孟德尔错误时,滑移突变,或沉默等位基因可能不能完全解释这种现象。有时候,它归因于染色体异常,例如单亲偏见(UPD)。这里,我们介绍了基于短串联重复序列(STR)检测(毛细管电泳平台)的亲子鉴定中两例可疑UPD的调查。案件1涉及三人,在孩子的6号染色体上检测到的所有基因型都是纯合的,并且在父亲中发现。案例2是一对(母亲和孩子),其中儿童3号染色体上的所有基因型都是纯合的,并不总是在母亲中发现。同时,在这两个染色体的特定基因座上也观察到孟德尔错误等位基因。此外,我们使用MGIEasy签名鉴定文库制备试剂盒在大规模平行测序平台上进行测序,其中包括普通常染色体,X和Y染色体,和用于法医实践的线粒体遗传标记。结果表明,两个平台上共享的STRs基因型一致,这两条染色体上的STRs和单核苷酸多态性(SNP)是纯合的。所有其他遗传标记都遵循遗传规律。综合分析支持孩子与被指控父母之间的亲子关系,观察到的遗传异常可归因于UPD。UPD很少发生,忽视它的存在会导致亲子鉴定中的错误排除,特别是当染色体上的多个基因座表现出纯合性时。
In paternity testing, when there are Mendelian errors in the alleles between the child and the parents, a slippage mutation, or silent allele may not fully explain the phenomenon. Sometimes, it is attributed to chromosomal abnormalities, such as uniparental disomy (UPD). Here, we present the investigation of two cases of suspected UPD in paternity testing based on short tandem repeat (STR) detection (capillary electrophoresis platform).
Case 1 involves a trio, where all genotypes detected on chromosome 6 in the child are homozygous and found in the father.
Case 2 is a duo (mother and child), where all genotypes on chromosome 3 in the child are homozygous and not always found in the mother. At the same time, Mendelian error alleles were also observed at specific loci in these two chromosomes. Furthermore, we used the MGIEasy Signature Identification Library Prep Kit for sequencing on the massively parallel sequencing platform, which included common autosomal, X and Y chromosomes, and mitochondrial genetic markers used in forensic practice. The results showed that the genotypes of shared STRs on the two platforms were consistent, and STRs and single nucleotide polymorphisms (SNPs) on these two chromosomes were homozygous. All other genetic markers followed the laws of inheritance. A comprehensive analysis supported the parent-child relationship between the child and the alleged parent, and the observed genetic anomalies can be attributed to UPD. UPD occurrences are rare, and ignoring its presence can lead to erroneous exclusions in paternity testing, particularly when multiple loci on a chromosome exhibit homozygosity.