Schneider Peter M, Bender Klaus, Mayr Wolfgang R, Parson Walther, Hoste Bernadette, Decorte Ronny, Cordonnier Jan, Vanek Daniel, Morling Niels, Karjalainen Matti, Marie-Paule Carlotti C, Sabatier Myriam, Hohoff Carsten, Schmitter Hermann, Pflug Werner, Wenzel Rainer, Patzelt Dieter, Lessig Rüdiger, Dobrowolski Peter, O'Donnell Geraldine, Garafano Luciano, Dobosz Marina, De Knijff Peter, Mevag Bente, Pawlowski Ryszard, Gusmão Leonor, Conceicao Vide Maria, Alonso Alonso Antonio, García Fernández Oscar, Sanz Nicolás Pilar, Kihlgreen Ann, Bär Walter, Meier Verena, Teyssier Anne, Coquoz Raphael, Brandt Conxita, Germann Ursula, Gill Peter, Hallett Justine, Greenhalgh Matthew
Institut für Rechtsmedizin, Universität Mainz, Mainz, Germany.
Forensic Sci Int. 2004 Jan 28;139(2-3):123-34. doi: 10.1016/j.forsciint.2003.10.002.
Degradation of human DNA extracted from forensic stains is, in most cases, the result of a natural process due to the exposure of the stain samples to the environment. Experiences with degraded DNA from casework samples show that every sample may exhibit different properties in this respect, and that it is difficult to systematically assess the performance of routinely used typing systems for the analysis of degraded DNA samples. Using a batch of artificially degraded DNA with an average fragment size of approx. 200 bp a collaborative exercise was carried out among 38 forensic laboratories from 17 European countries. The results were assessed according to correct allele detection, peak height and balance as well as the occurrence of artefacts. A number of common problems were identified based on these results such as strong peak imbalance in heterozygous genotypes for the larger short tandem repeat (STR) fragments after increased PCR cycle numbers, artefact signals and allelic drop-out. Based on the observations, strategies are discussed to overcome these problems. The strategies include careful balancing of the amount of template DNA and the PCR cycle numbers, the reaction volume and the amount of Taq polymerase. Furthermore, a careful evaluation of the results of the fragment analysis and of automated allele calling is necessary to identify the correct alleles and avoid artefacts.
从法医样本中提取的人类DNA发生降解，在大多数情况下是由于样本暴露于环境中而导致的自然过程。来自实际案件样本的降解DNA的经验表明，每个样本在这方面可能表现出不同的特性，并且难以系统地评估常规使用的分型系统对降解DNA样本进行分析的性能。利用一批平均片段大小约为200 bp的人工降解DNA，来自17个欧洲国家的38个法医实验室开展了一项协作实验。根据正确的等位基因检测、峰高和平衡以及假象的出现情况对结果进行评估。基于这些结果确定了一些常见问题，如在增加PCR循环数后，较大的短串联重复序列（STR）片段在杂合基因型中出现强烈的峰不平衡、假象信号和等位基因缺失。基于这些观察结果，讨论了克服这些问题的策略。这些策略包括仔细平衡模板DNA的量和PCR循环数、反应体积和Taq聚合酶的量。此外,有必要对片段分析结果和自动等位基因分型进行仔细评估，以识别正确的等位基因并避免假象。
