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首页> 外文期刊>Forensic science international. Genetics >Improving the efficacy of the standard DNA differential extraction method for sexual assault evidence
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Improving the efficacy of the standard DNA differential extraction method for sexual assault evidence

机译：提高性攻击证据标准DNA差分提取方法的疗效

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The efficacy of a DNA differential extraction procedure relies on reducing the amount of non-sperm female DNA carryover into the sperm fraction, while providing a sufficient recovery of male DNA from the sperm cell component. A standard approach to this extraction is to use a mild initial lysis step to digest the female (epithelial cell) component in the mixture, followed by a series of centrifugation and wash steps to further purify the resulting sperm-pellet fraction. This sperm fraction is then digested in the presence of a chemical reducing agent in preparation for DNA extraction. This method has been employed with relatively few changes since its introduction in the mid-1980s, despite numerous attempts to develop new or improved procedures. In this report, we demonstrate that it is possible to improve the efficacy of the standard differential extraction by applying simple modifications that can reduce the amount of female DNA carryover into the sperm fraction, with no adverse effects on the recovery of male DNA. In one modification, the addition of a second mild lysis step at the beginning of the differential extraction procedure improved the average male-to-female DNA ratio in the sperm fraction by 3- to 6-fold. In another modification, a "tube transfer" step was added to move the re-suspended sperm pellet to a new tube for the second mild lysis and subsequent wash steps. With this modification, the average male-to-female DNA ratio in the sperm fraction was improved by 4- to 90-fold, relative to results obtained for the non-modified differential extraction method. These modifications may be accomplished using tools and reagents that are already present in most forensic DNA laboratories, so that implementation should be relatively low-cost and practical.
机译：DNA差分提取方法的功效依赖于将非精子雌性DNA携带的量降低到精子级分中，同时提供来自精子细胞组分的雄性DNA的充分恢复。该提取的标准方法是使用温和的初始裂解步骤来消化混合物中的雌性（上皮细胞）组分，然后用一系列离心和洗涤步骤进一步纯化所得的精子颗粒馏分。然后在制备DNA提取的化学还原剂存在下消化该精子级分。尽管有许多尝试开发新的或改进的程序，但这种方法已经采用了20世纪80年代中期的介绍以来的变化相对较少。在本报告中，我们证明通过应用可以将雌性DNA携带量降低到精子级分的简单修饰，可以提高标准差异提取的功效，对雄性DNA的回收没有不利影响。在一个修饰中，在差分提取过程开始时添加第二温和裂解步骤，将精子馏分的平均雄性血对叶片分数3至6倍改善。在另一个修改中，加入“管转移”步骤以将再悬浮的精子颗粒移动到用于第二温和裂解的新管和随后的洗涤步骤。通过这种改性，相对于未修饰的差分提取方法获得的结果，精子级分中的平均映像DNA比例提高了4-至90倍。可以使用已经存在于最常规的DNA实验室中已经存在的工具和试剂来完成这些修改，因此实施应该是相对低成本和实用的。

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