Institut für Medizinische Informatik und Statistik, Christian-Albrechts-Universität Kiel, Brunswiker Straße 10, 24105 Kiel, Germany.
Forensic Sci Int Genet. 2012 Dec;6(6):778-84. doi: 10.1016/j.fsigen.2012.02.015. Epub 2012 Mar 27.
A large number of short tandem repeat (STR) markers spanning the entire human X chromosome have been described and established for use in forensic genetic testing. Due to their particular mode of inheritance, X-STRs often allow easy and informative haplotyping in kinship analyses. Moreover, some X-STRs are known to be tightly linked so that, in combination, they constitute even more complex genetic markers than each STR taken individually. As a consequence, X-STRs have proven particularly powerful in solving complex cases of disputed blood relatedness. However, valid quantification of the evidence provided by X-STR genotypes in the form of likelihood ratios requires that the recombination rates between markers are exactly known. In a collaborative family study, we used X-STR genotype data from 401 two- and three-generation families to derive valid estimates of the recombination rates between 12 forensic markers widely used in forensic testing, namely DXS10148, DXS10135, DXS8378 (together constituting linkage group I), DXS7132, DXS10079, DXS10074 (linkage group II), DXS10103, HPRTB, DXS10101 (linkage group III), DXS10146, DXS10134 and DXS7423 (linkage group IV). Our study is the first to simultaneously allow for mutation and recombination in the underlying likelihood calculations, thereby obviating the bias-prone practice of excluding ambiguous transmission events from further consideration. The statistical analysis confirms that linkage groups I and II are transmitted independently from one another whereas linkage groups II, III and IV are characterised by inter-group recombination fractions that are notably smaller than 50%. Evidence was also found for recombination within all four linkage groups, with recombination fraction estimates ranging as high as 2% in the case of DXS10146 and DXS10134.
大量的短串联重复序列（STR）标记跨越整个人类 X 染色体已被描述和建立，用于法医遗传学检测。由于其特定的遗传模式，X-STR 通常允许在亲属关系分析中进行简单而信息丰富的单体型分析。此外，一些 X-STR 已知紧密连锁，因此，组合起来，它们构成的遗传标记比每个单独的 STR 更为复杂。因此，X-STR 在解决复杂的血缘关系争议案件方面证明特别有效。然而，以似然比的形式对 X-STR 基因型提供的证据进行有效量化，需要确切地知道标记之间的重组率。在一项合作的家庭研究中，我们使用来自 401 个两代和三代家庭的 X-STR 基因型数据，得出了广泛用于法医检测的 12 个法医标记之间的有效重组率估计值，即 DXS10148、DXS10135、DXS8378（共同构成连锁群 I）、DXS7132、DXS10079、DXS10074（连锁群 II）、DXS10103、HPRTB、DXS10101（连锁群 III）、DXS10146、DXS10134 和 DXS7423（连锁群 IV）。我们的研究首次在基础似然计算中同时允许突变和重组，从而避免了将模糊的传递事件排除在进一步考虑之外的易产生偏差的做法。统计分析证实，连锁群 I 和 II 彼此独立传递，而连锁群 II、III 和 IV 的组间重组分数明显小于 50%。还发现了所有四个连锁群内的重组证据，在 DXS10146 和 DXS10134 的情况下，重组分数估计高达 2%。
