Oldoni Fabio, Castella Vincent, Grosjean Frederic, Hall Diana
Unité de Génétique Forensique, Centre Universitaire Romand de Médecine Légale, Centre Hospitalier Universitaire Vaudois et Université de Lausanne, Ch. de la Vulliette 4, 1000 Lausanne, Switzerland.
Unité de Génétique Forensique, Centre Universitaire Romand de Médecine Légale, Centre Hospitalier Universitaire Vaudois et Université de Lausanne, Ch. de la Vulliette 4, 1000 Lausanne, Switzerland.
Forensic Sci Int Genet. 2017 May;28:111-117. doi: 10.1016/j.fsigen.2017.02.004. Epub 2017 Feb 14.
Casework samples collected for forensic DNA analysis can produce genomic mixtures in which the DNA of the alleged offender is masked by high quantities of DNA coming from the victim. DIP-STRs are novel genetic markers specifically developed to enable the target analysis of a DNA of interest in the presence of exceeding quantities of a second DNA (up to 1000-fold). The genotyping system, which is based on allele-specific amplifications of haplotypes formed by a deletion/insertion polymorphism (DIP) and a short tandem repeat (STR), combines the capacity of targeting the DNA of an individual with a strong identification power. Finally, DIP-STRs are autosomal markers therefore they can be applied to any combination of major and minor DNA. In this study we aimed to assess the ability of DIP-STRs to detect the minor contributor on challenging "touch" DNA samples simulated with representative crime-associated substrates and to compare their performance to commonly used male-specific markers (Y-STRs). As part of a comprehensive study on the relative DNA contribution of two persons handling the same object, we selected 71 unbalanced contact traces of which 14 comprised a male minor DNA contributor mixed to a female major DNA contributor. Using a set of six DIP-STRs, one to four markers were found to be informative for the minor DNA detection across traces. When compared to Y-STRs (14 traces), the DIP-STRs showed similar sensitivity in detecting the minor DNA across substrate materials with a similar occurrence of allele drop-out. Conversely, because of the sex combination of the two users of the object, 57 remaining traces could only be investigated by DIP-STRs. Of these, 30 minor DNA contributors could be detected by all informative markers while 12 traces showed events of allele drop-out. Finally, 15 traces showed no amplification of the minor DNA. These last 15 samples were mostly characterized by a combination of short handling time of the object, low DNA recovery and/or one single informative DIP-STR. In conclusion, the DIP-STRs represent alternative markers to help solving unbalanced two-source DNA mixtures, and also those produced from contact stains. These markers, in addition to a novel set of 10 DIP-STRs specifically developed according to forensic technical standards, will offer a valuable tool complementary to Y-STR markers.
为法医DNA分析采集的案例样本可能会产生基因组混合物，其中犯罪嫌疑人的DNA会被来自受害者的大量DNA掩盖。双插入/缺失短串联重复序列（DIP-STR）是专门开发的新型遗传标记，能够在存在过量第二种DNA（高达1000倍）的情况下对感兴趣的DNA进行靶向分析。该基因分型系统基于由缺失/插入多态性（DIP）和短串联重复序列（STR）形成的单倍型的等位基因特异性扩增，将靶向个体DNA的能力与强大的识别能力结合在一起。最后，DIP-STR是常染色体标记，因此它们可应用于任何主要和次要DNA的组合。在本研究中，我们旨在评估DIP-STR在具有挑战性的“接触”DNA样本上检测次要贡献者的能力，这些样本是用具有代表性的犯罪相关底物模拟的，并将其性能与常用的男性特异性标记（Y-STR）进行比较。作为对处理同一物体的两人相对DNA贡献的全面研究的一部分，我们选择了71个不平衡的接触痕迹，其中14个包含与女性主要DNA贡献者混合的男性次要DNA贡献者。使用一组六个DIP-STR，发现一到四个标记对于跨痕迹检测次要DNA具有信息价值。与Y-STR（14个痕迹）相比，DIP-STR在检测跨底物材料的次要DNA方面表现出相似的灵敏度，等位基因缺失发生率相似。相反，由于物体的两个使用者的性别组合，其余57个痕迹只能通过DIP-STR进行研究。其中，30个次要DNA贡献者可被所有信息性标记检测到，而12个痕迹显示出等位基因缺失事件。最后，15个痕迹显示次要DNA未扩增。最后这15个样本的主要特征是物体处理时间短、DNA回收率低和/或只有一个信息性DIP-STR。总之，DIP-STR是有助于解决不平衡的双源DNA混合物以及接触污渍产生的混合物的替代标记。这些标记，除了根据法医技术标准专门开发的一组新的10个DIP-STR外，还将提供一种与Y-STR标记互补的有价值工具。
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