Ge Jianye, Budowle Bruce
Institute of Applied Genetics, Department of Forensics and Investigative Genetics, University of North Texas Health Science Center, Fort Worth, TX, USA,
Int J Legal Med. 2014 Mar;128(2):259-67. doi: 10.1007/s00414-013-0924-6. Epub 2013 Oct 5.
There are generally two strategies for low template DNA typing: the complete strategy, which uses all available DNA in a single PCR and subsequent typing, and the consensus strategy, in which the biological sample is divided into two or more aliquots and the genotype profile is determined by consensus from these "replicates." In this study, the consensus and complete strategies are compared by a statistical approach in terms of the accuracy of obtaining the correct genotype at a single locus for single source samples. Logistic models were employed to describe the allele drop-out and drop-in events. The parameters of the models were estimated with empirical or hypothetical data. The probabilities of obtaining the true genotype and the chances to observe drop-out and drop-in alleles were estimated and compared for both strategies. Consistent with a previous experimental study, this study found that, with relatively high input DNA (e.g., ≥ 100 pg), the complete strategy performs better than the consensus strategy to obtain the true genotype and the complete strategy will display less dropped out alleles. The consensus strategy had less drop-in alleles for ≤ 100 pg DNA samples. Moreover, the limitations of the logistic models were discussed. Ideal models with better fit of empirical data approximating casework conditions were proposed for future studies.
低模板DNA分型通常有两种策略：完整策略，即在一次聚合酶链反应（PCR）及后续分型中使用所有可用的DNA；以及一致性策略，即将生物样本分成两个或更多份，通过这些“重复样本”的一致性来确定基因型谱。在本研究中，通过统计方法比较了一致性策略和完整策略在单源样本单个位点获取正确基因型的准确性。采用逻辑模型来描述等位基因缺失和插入事件。模型参数通过经验数据或假设数据进行估计。对两种策略获得真实基因型的概率以及观察到等位基因缺失和插入的机会进行了估计和比较。与先前的实验研究一致，本研究发现，在输入DNA相对较高（例如，≥100 pg）时，完整策略在获得真实基因型方面比一致性策略表现更好，并且完整策略显示出的缺失等位基因更少。对于DNA样本≤100 pg的情况，一致性策略的插入等位基因更少。此外，还讨论了逻辑模型的局限性。提出了更适合近似实际案件情况的经验数据的理想模型以供未来研究使用。
