STR melting curve analysis as a genetic screening tool for crime scene samples

In this proof-of-concept study, high-resolution melt curve (HRMC) analysis was investigated as a postquantification screening tool to discriminate human CSF1PO and THO1 genotypes amplified with mini-STR primers in the presence of SYBR Green or LCGreen Plus dyes. A total of 12 CSF1PO and 11 HUMTHO1 genotypes were analyzed on the LightScanner HR96 and LS-32 systems and were correctly differentiated based upon their respective melt profiles. Short STR amplicon melt curves were affected by repeat number, and single-source and mixed DNA samples were additionally differentiated by the formation of heteroduplexes. Melting curves were shown to be unique and reproducible from DNA quantities ranging from 20 to 0.4 ng and distinguished identical from nonidentical genotypes from DNA derived from different biological fluids and compromised samples. Thus, a method is described which can assess both the quantity and the possible probative value of samples without full genotyping.     

中国汉族人群17个Y-STR基因座突变情况分析

目的 调查分析17个Y-STR基因座等位基因突变的情况.方法 收集中国汉族人群867对父子共1 649份男性血样本.采用YfilerTM复合扩增试剂盒进行17个Y-STR基因座分型,共检测出14 739次等位基因传递,统计各基因座发生等位基因突变的频率.结果 在17个基因座中发现涉及13个基因座共41次突变,其中一步突变40次(97.6％),两步突变1次(2.4％);突变共涉及40对父子,其中39对仅1个基因座发生突变(97.5％),1对同时有2个基因座发生突变(2.5％);平均突变率为2.8×10-3(95％CI 2.0～3.8×10-3).等位基因突变时获得重复单位数19次,丢失重复单位数22次,两者比例接近.结论 中国汉族人群Y-STR基因座突变可涉及多数基因座,突变率在2.8×10-3左右,在数据库的建立与应用中应重视,注意采用相关方法进行甄别.     

Development of a rapid, 96-well alkaline based differential DNA extraction method for sexual assault evidence

We present a rapid alkaline lysis procedure for the extraction of DNA from sexual assault evidence that generates purified sperm fraction extracts that yield STR typing results similar to those obtained from the traditional organic/dithiothreitol differential extraction. Specifically, a sodium hydroxide based differential extraction method has been developed in a single-tube format and further optimized in a 96-well format. The method yields purified extracts from a small sample set (∼2-6 swabs) in approximately 2 h and from a larger sample set (up to 96 swabs) in approximately 4 h. While conventional differential extraction methods require vigorous sample manipulation to remove the spermatozoa from the substrate, the method described here exploits the propensity of sperm to adhere to a substrate and does not require any manipulation of the substrate after it is sampled. For swabs, sample handling is minimized by employing a process where the tip of the swab, including the shaft, is transferred to the appropriate vessel eliminating the need for potentially hazardous scalpels to separate the swab material from the shaft. The absence of multiple handling steps allows the process to be semi-automated, however the procedure as described here does not require use of a robotic system. This method may provide forensic laboratories a cost-effective tool for the eradication of backlogs of sexual assault evidence, and more timely service to their client agencies. In addition, we have demonstrated that a modification of the procedure can be used to retrieve residual sperm-cell DNA from previously extracted swabs.     

Challenging DNA: Assessment of a range of genotyping approaches for highly degraded forensic samples

It is common in forensic casework to encounter highly degraded DNA samples from a variety of sources. In this category bone and teeth samples are often the principal source of evidential material for criminal investigations or identification of long-deceased individuals. In these circumstances standard STRs are prone to fail due to their long amplicon sizes (since DNA becomes progressively more fragmented as it degrades). To successfully resolve such cases alternative markers can be used and until recently the only other tool available was mitochondrial DNA, which despite being more resistant to degradation, is much less informative. A rapidly developing approach to analyzing degraded DNA is the typing of loci from short-amplicon PCR products based on markers such as mini-STRs and autosomal SNPs. We have performed an analysis of several cases with naturally degraded DNA using established STRs plus mini-STRs and autosomal SNPs in order to make an objective comparison of the performance of each method using challenging DNA. The main aim was to establish the benefits and drawbacks of each marker set to help the practitioner choose the DNA analysis method most suited to the circumstances of each case.     

资产专用性视角的产业集群竞争优势研究——日本汽车产业集群的分析与启示

与美国的汽车产业相比,日本汽车产业集群具有低交易成本与高专用性双重优势,对美日汽车产业集群的比较分析可以为我国区域经济发展的产业集群战略提供借鉴与指导。政府的产业规划不仅是产业区域发展的地理空间规划(工业园区、开发区建设),更应该是企业间分工的产业价值链规划;政府的经济干预不应该局限在税收等产业政策的安排,更应该注重以信誉为核心的制度建设。     

STR基因座与Amelogenin的峰面积比在DNA降解评估中的应用

目的研究DNA降解过程中STR基因座与性别基因座Amelogenin(AMEL)峰面积比(STR/AMEL)的变化规律,探讨STR/AMEL值在评估DNA降解程度中的应用。方法取人体髂腰肌组织抽提DNA,分析DNaseⅠ酶人工降解后STR/AMEL值(Penta E/AMEL、Penta D/AMEL、FGA/AMEL)的变化,并分析室外环境自然降解的髂腰肌组织中三者比值的变化。以降解时间为自变量(x),STR/AMEL值为因变量(y),进行回归曲线分析,建立两种条件下三组曲线方程。结果人工降解及自然降解条件下STR/AMEL值与降解时间均呈负相关,一元三次方程能够较好地模拟STR/AMEL值随降解时间的变化规律。人工降解条件下,R~2均大于0.99;自然降解条件下,R~2均大于0.86。结论 STR/AMEL值(Penta E/AMEL、Penta D/AMEL、FGA/AMEL)与DNA降解程度呈负相关,有望应用于DNA降解程度的评估。     

p33.4位点扩增片段长度多态性及其法医学应用的研究

以聚合酶链反应（PCR）、聚丙烯酰胺凝胶垂直电泳和银染法对中国100名无关个体小卫星区域p33．4位点的扩增片段长度多态性（Amp－FLPs）进行了研究，检出了8个等位基因。通过BIOTRAC系统进行数据处理．各等位基因重复单位的数目分别为7、10到15，其中在13～14之间发现一差值不足一个重复单位长度的罕见等位基因。片段长度分布于603～1115bP之间，基因频率分布于0.5～33．5％间，杂合度为64％，DP值为84．5％。对5个家庭25名相关个体进行分析，符合孟德尔遗传定律；对同一个体不同组织的DNA进行P33.4位点的分型研究表明，该技术适宜于法医物证检验。此外，本研究以Chelex处理不同检材制备DNA模板用于扩增，率先建立了比常规方法更快、更简便、更为实用的检验方法。     

Quantitation of human genomic DNA through amplification of the amelogenin locus

An alternate method for quantitation of human genomic DNA is presented. Quantitative template amplification technology (abbreviated "Q-TAT") estimates the quantity of human DNA present in an extract by comparing fluorescence in X and Y amplicons produced from unknowns with fluorescence in a standard curve amplified from known quantities of reference DNA. Q-TAT utilizes PCR and electrophoresis with fluorescent detection/quantitation, precluding the need for new instrumentation, methodology, or quality assurance associated with slot-blot or real-time PCR. In a comparison study incorporating shared samples, Q-TAT was found to be more sensitive than widely used slot-blot methods but somewhat less sensitive than real-time PCR. Among samples containing DNA concentrations ranging from 100 pg/microL to 2-4 ng/microL, Q-TAT produced DNA concentration estimates that agreed reasonably well with either Quantiblot or real-time PCR. Q-TAT was reproducible with a typical coincidence of variation of about 35%. Quantitation of human DNA in this study involved summing fluorescence in X and Y amplicons in unknowns and quantitation standards. However, analyzing fluorescence in X and Y amplicons individually could allow estimates of male and female DNA present in mixtures to be made. Moreover, since X and Y amplicons exhibit sizes of 210 and 216 bp, respectively, the integrity as well as the concentration of the genomic DNA template can be assessed. Q-TAT represents an alternate method useful for the quantitation of human genomic DNA prior to amplification of STR loci used for identity testing purposes. The method uses existing equipment and procedures in conjunction with a well-characterized DNA standard to produce concentration estimates for unknowns that reliably produce STR profiles suitable for analysis.