牙髓细胞DNA含量与死后经过时间的相关性

目的探讨死后不同环境温度下离体牙的牙髓细胞平均DNA含量变化与死后时间(PM I)的相关性。方法采用细胞图像分析系统(PIPS-2020),测定离体即刻至15d牙齿在低温环境(10~15℃)和高温(30~35℃)环境下牙髓细胞DNA含量变化值,并对其数据进行统计学分析。结果在不同的环境温度下,牙髓细胞DNA降解的速度有所不同,温度的升高有加速牙髓细胞DNA降解的趋势,且DNA降解存在一个平台期。低温组牙髓细胞平均DNA含量与PM I之间的相关系数r=0.953,相关指数R2=0.917;高温组的相关系数r=0.991,相关指数R2=0.971。结论牙髓细胞平均DNA含量与PM I之间具有高度相关性,测定牙髓细胞的DNA变化情况对推断3d(高温环境)或6d(低温环境)后的PM I有参考价值。     

国人六个高变DNA位点的基因频率分布

使用6个单位点探针，用Southern印迹杂交技术研究了国人的D2S44，D17S79，D14S13，D14S1，DXYS14及D18S27等位点的基因频率分布。发现它们的DNA指纹图均具高度多态性，等位基因数27～107个。非父排除率（EPP）分别为0．8407、0．7691、0．9792、0．9040、0．9400及0．8177，累积非父排除率为0．99999；个人识别能力（DP）分别为0.9880、0.9766，0.9996，0.9961，0.9973及0．9338，累积个人识别能力接近1，故可作为亲子鉴定及个人识别非常有力的工具。此外还对单位点探针的优缺点进行了讨论。     

用引物Y_3、Y_4和PCR方法鉴定性别的法医学应用

用Y3、Y4和Alu9．1、Alug．2两对引物和PCR方法检测陈旧血痕和毛根的性别获得成功。引物Y3、Y4扩增的靶序列位于Y染色体特异3．4Kb重复序列中，扩增产物为460bp；引物Alu9．1、Alu9.2用以扩增男女共有的Alu重复序列，扩增产物为130bP。室温保存13年之久的19例脐带血血痕（男性9冽，女性10例）和室温保存10～11个月的10例已知性别自然脱落毛根（男性6例，女性4例）的性别测定结果均正确；对一起凶杀案的血痕性别测定为定案提供了重要证据。本方法简化了样品的前处理过程。     

利用DNA破案2例

1案件简介 2006年11月13日，马迹镇杉山村公路地段发生一起交通事故，受害人曹某（男，10岁）当场死亡。肇事车辆逃逸，在侦查中发现一外地大货车有重大嫌疑，而该车驾驶员失口否认，其他没有任何人证物证。     

Swabs as DNA Collection Devices for Sampling Different Biological Materials from Different Substrates

Currently, there is a variety of swabs for collection of biological evidence from crime scenes, but their comparative efficiency is unknown. Here, we report the results of an investigation into the efficiency of different swab types to collect blood, saliva and touch DNA from a range of substrates. The efficiency of extracting blood and saliva from each swab type was also tested. Some swabs were significantly more effective than others for sampling biological materials from different substrates. Swabs with the highest sampling efficiency, however, often did not have the highest extraction efficiency. Observations were recorded regarding practicality of each swab in a variety of situations. Our study demonstrates that selection of sampling device impacts greatly upon successful collection and extraction of DNA. We present guidelines to assist in evaluation of swab choice.     

Modeling Forensic DNA Database Performance*

Abstract: Over the past decade or more, DNA databases have been a focal point of development for the forensic field. Using this approach, forensic and law enforcement agencies have aided millions of investigations, many of which would remain unsolved but for the intelligence links provided from DNA database comparison. However, despite their widespread use and increasingly broad legislative and operational reach, there has been limited overarching performance modeling or reflection on drivers of operational or financial efficiency. This study derives an inferential model for DNA database performance using data from major national DNA database programs. Parameters that optimize desirable database outputs (matches) are isolated and discussed, as is an approach for maximizing financial efficiency and minimizing ethical impact. This research takes important steps toward identifying measures of performance for forensic DNA database operations.     

Validation of SRY Marker for Forensic Casework Analysis

Abstract:  Determining the gender of the source of forensic DNA evidence is based on the amelogenin test. However, at times the assay may not be indicative of gender assignment, because of deletions at the amelogenin site. Previously, we described successful coamplification of a marker residing within the SRY gene with the short tandem repeat markers from two commercially available human identification kits. The study herein addresses the validation of primers for the target SRY gene regarding specificity, sensitivity, and robustness. Among 115 unrelated male Slovenians no null allele was observed. Repeatable and reliable results were obtained from as little as 25 pg of template DNA, indicating a high sensitivity of detection for the assay. No polymerase chain reaction product was observed even at a concentration of 10 ng/μL of template female DNA. Additionally, the male specific marker could be detected in mixed male and female samples down to a ratio of 1:16.     

Sequencing of mitochondrial DNA and the problem of human specificity

When analysing trace materials and degraded DNA the issue of human specificity is highly important. Especially when it comes down to the analysis of mitochondrial DNA which is extremely susceptible to contamination authenticity is the main question. Therefore in the presented study mitochondrial primers were tested on their human specificity. In all cases it was possible to amplify DNA of animals with human mt-primers. These unintentional amplifications could only be decreased by choosing austere PCR parameters. The study implies the importance of comprehensive evaluation of primers, chemicals and PCR parameters.     

A novel method for ABO genotyping using a DNA chip

ABO genotyping is often performed to identify the blood type of decomposed samples, which is difficult to be determined by a serological test. In this study, we developed a simple method for ABO genotyping using a DNA chip. In this method, polymerase chain reaction-amplified and fluorescent-labeled fragments in the ABO gene and primate-specific D17Z1 were hybridized with DNA probes on a chip designed to detect single nucleotide polymorphisms (SNPs) in the ABO gene and part of the D17Z1 sequence. Using blood samples from 42 volunteers and 10 animal species, we investigated whether the chip could be used to detect SNPs in the ABO gene and the D17Z1 sequence. This method was then applied to various forensic samples, and it was confirmed that this method was suitable for the simultaneous analyses of ABO genotyping and species identification. This method fulfills the recent need for the development of rapid and convenient methods for criminal investigations.     

Simplified field preservation of tissues for subsequent DNA analyses

Successful DNA-based identification of mass disaster victims depends on acquiring tissues that are not highly degraded. In this study, multiple protocols for field preservation of tissues for later DNA analysis were tested. Skin and muscle samples were collected from decaying pig carcasses. Tissues were preserved using cold storage, desiccation, or room temperature storage in preservative solutions for up to 6 months. DNA quality was assessed through amplification of successively larger segments of nuclear DNA. Solution-based storage, including a DMSO/NaCl/EDTA mixture, alcohols, and RNAlater preserved DNA of the highest quality, refrigeration was intermediate, and desiccation was least effective. Tissue type and extent of decomposition significantly affected stored DNA quality. Overall, the results indicate that any tissue preservation attempt is far superior to delaying or forgoing preservation efforts, and that simple, inexpensive methods can be highly effective in preserving DNA, thus should be initiated as quickly as possible.