Phillips C, Fondevila M, García-Magariños M, Rodriguez A, Salas A, Carracedo A, Lareu M V
Forensic Genetics Unit, Institute of Legal Medicine, University of Santiago de Compostela, Spain.
Forensic Sci Int Genet. 2008 Jun;2(3):198-204. doi: 10.1016/j.fsigen.2008.02.002. Epub 2008 Apr 18.
When using a standard battery of STRs for relationship testing a small proportion of analyses can give ambiguous results - where the claimed relationship cannot be confirmed by a high enough paternity index or excluded with fully incompatible genotypes. The majority of such cases arise from unknowingly testing a brother of the true father and observing only a small number of exclusions that can each be interpreted as one- or two-step mutations. Although adding extra STRs might resolve a proportion of cases, there are few properly validated extra STRs available, while the commonly added hypervariable SE33 locus is four times more mutable than average, increasing the risk of ambiguous results. We have found SNPs in large multiplexes are much more informative for both low initial probabilities or ambiguous exclusions and at the same time provide a more reliable genotyping approach for the highly degraded DNA encountered in many identification cases. Eight relationship cases are outlined where the addition of SNP data resolved analyses that had remained ambiguous even with extended STR typing. In addition we have made simulations to ascertain the frequency of failing to obtain exclusions or conclusive probabilities of paternity with different marker sets when a brother of the true father is tested. Results indicate that SNPs are statistically more efficient than STRs in resolving cases that distinguish first-degree relatives in deficient pedigrees.
在使用标准的短串联重复序列（STR）组合进行亲缘关系检测时，一小部分分析可能会得出模糊的结果——即声称的亲缘关系无法通过足够高的父权指数得到证实，或者无法被完全不相容的基因型排除。大多数此类情况是由于在不知情的情况下检测了真正父亲的兄弟，并且只观察到少量的排除情况，而这些排除情况中的每一种都可能被解释为一步或两步突变。虽然添加额外的STR可能会解决一部分案例，但可用的经过适当验证的额外STR很少，而通常添加的高变区SE33位点的突变率是平均水平的四倍，增加了结果模糊的风险。我们发现，在大型多重检测中，单核苷酸多态性（SNP）对于低初始概率或模糊排除情况都更具信息性，同时为许多鉴定案例中遇到的高度降解的DNA提供了一种更可靠的基因分型方法。本文概述了八个亲缘关系案例，其中添加SNP数据解决了即使进行了扩展STR分型仍模糊不清的分析。此外，我们进行了模拟，以确定在检测真正父亲的兄弟时，使用不同标记集未能获得排除结果或确定父权概率的频率。结果表明，在解决区分缺陷谱系中一级亲属的案例时，SNP在统计学上比STR更有效。
