Department of Forensic Genetics and Forensic Toxicology, National Board of Forensic Medicine, Linköping, Sweden.
Department of Forensic Genetics and Forensic Toxicology, National Board of Forensic Medicine, Linköping, Sweden; Department of Clinical and Experimental Medicine, Faculty of Health Sciences, Linköping University, Linköping, Sweden.
Forensic Sci Int Genet. 2019 Mar;39:44-49. doi: 10.1016/j.fsigen.2018.11.020. Epub 2018 Nov 28.
The recent year's development of massively parallel sequencing (MPS) instruments and assays have now made it a compatible complement to the established capillary electrophoresis (CE) analysis for different forensic genetic applications. It is well known that short tandem repeat (STR) alleles of the same fragment size could have different DNA sequences. Thus, there will be an expected increase in the population genetic diversity for the present set of forensic STRs when performing the analysis with MPS technologies and taking the internal DNA sequence into account. In order to study the additional value of this increase of information for kinship analysis casework, we set up an allele frequency database for the Swedish population for the autosomal markers included in the ForenSeq™ DNA Signature Prep Kit (Illumina). A total of 298 individuals with Swedish origin were analyzed and allele frequency distributions based on DNA sequence polymorphisms for 27 autosomal STRs were established. As expected, the results showed an addition in number of observed alleles with 55% in total compared with fragment length based allele definitions, however, a majority only appeared in a few number of observations. In addition, simulations were performed in order to study the impact of the increase in number of observed alleles for the expected likelihood ratios (LRs) for different kinship case scenarios. Only a minor increase of the LRs were, however, observed when taking allele sequence variations in addition with fragment length variations into account compared to only considering fragment length variations. Further studies are required to see if it is cost effective to implement this technique that, according to this study, only has a limited overall additive effect for kinship testing. Although, in specific cases MPS methods will increase the discrimination power due to that, even if in a low frequency, a high genetic diversity exist and the differentiation could be more significant. The establishment of the allele frequency database will enable biostatistical calculations to be performed in casework.
近年来，大规模平行测序（MPS）仪器和检测方法的发展，使其成为与传统毛细管电泳（CE）分析在不同法医遗传学应用中兼容互补的方法。众所周知，相同片段大小的短串联重复（STR）等位基因可能具有不同的 DNA 序列。因此，当使用 MPS 技术进行分析并考虑内部 DNA 序列时，当前法医 STR 组的群体遗传多样性预计会增加。为了研究这种信息增加对亲属关系分析案例工作的额外价值，我们为包含在 ForenSeq™ DNA Signature Prep Kit（Illumina）中的常染色体标记物建立了一个瑞典人群的等位基因频率数据库。共分析了 298 名具有瑞典血统的个体，并根据基于 DNA 序列多态性的 27 个常染色体 STR 建立了等位基因频率分布。正如预期的那样，结果显示与基于片段长度的等位基因定义相比，观察到的等位基因数量增加了 55%，但大多数仅在少数观察中出现。此外，还进行了模拟，以研究增加观察到的等位基因数量对不同亲属关系案例情况下预期似然比（LR）的影响。与仅考虑片段长度变化相比，当同时考虑等位基因序列变化和片段长度变化时，LR 仅略有增加。需要进一步的研究来确定是否值得实施该技术，根据这项研究，该技术仅对亲属关系测试具有有限的总体附加效果。尽管如此，在特定情况下，由于存在高度的遗传多样性，即使频率较低，MPS 方法也会增加鉴别力，并且区分可能更为显著。等位基因频率数据库的建立将使案件中的生物统计计算得以进行。
