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.     

New optimized DNA extraction protocol for fingerprints deposited on a special self-adhesive security seal and other latent samples used for human identification

Abstract: Obtaining complete short tandem repeat (STR) profiles from fingerprints containing minimal amounts of DNA, using standard extraction techniques, can be difficult. The aim of this study was to evaluate a new kit, Fingerprint DNA Finder (FDF Kit), recently launched for the extraction of DNA and STR profiling from fingerprints placed on a special device known as Self‐Adhesive Security Seal Sticker^® and other latent fingerprints on forensic evidentiary material like metallic guns. The DNA extraction system is based on a reversal of the silica principle, and all the potential inhibiting substances are retained on the surface of a special adsorbent, while nucleic acids are not bound and remain in solution dramatically improving DNA recovery. DNA yield was quite variable among the samples tested, rendering in most of the cases (>90%) complete STR profiles, free of PCR inhibitors, and devoid of artifacts. Even samples with DNA amount below 100 pg could be successfully analyzed.     

Detection of genotype recycling fraud in U.S. immigrants

Abstract: Relationship testing laboratories provide genetic evidence to support or refute claims of kinship between U.S. citizen petitioners and potential immigrant beneficiaries. One female beneficiary presented a male amelogenin type and alleles at 15 autosomal loci that were identical to an alleged brother’s. Laboratory records showed that her alleged father had petitioned to have 15 children emigrate from Ghana. The petitioner’s 15 paternity indices exceeded 10⁵, but the children shared only four short tandem repeat (STR) profiles, suggesting fraudulent reuse of genotypes in this alleged pedigree (AP). To determine the extent of this “genotype recycling,” I examined the laboratory’s 555 APs from Ghana and 532 control APs from Nigeria. Seventeen Ghanaian APs (3.1%) but no Nigerian APs showed genotype recycling. Of 90 tested people in the 17 APs, 56 shared identical STR profiles with others in their AP. Of these 56 people, 10 were petitioners with unexpectedly high parentage indices. Seven of 56 had amelogenin types that disagreed with their declared genders. Database searches for identical multilocus genotypes in allegedly different people would best detect this fraud.     

Development of a DNA-based macroarray for the detection and identification of Amanita species

A DNA-based macroarray was designed to quickly and accurately identify certain Amanita mushroom specimens at the species level. The macroarray included probes for Amanita phalloides and Amanita ocreata, toxic species responsible for most mushroom poisonings, and Amanita lanei and Amanita velosa, edible species sometimes confused with toxic species, based on sequences of the highly variable internal transcribed spacer (ITS) region of rDNA. A cryptic species related to A. ocreata and one related to A. lanei, identifiable by ITS sequences, were also included. Specific multiple oligonucleotide probes were spotted onto nylon membranes and the optimal hybridization temperatures were determined. The Amanita DNA array was highly specific, sensitive (0.5 ng DNA/μL and higher were detected), and reproducible. In two case studies, the method proved useful when only small amounts of mushroom tissue remained after a suspected poisoning. An identification could be completed in 12 h.     

激光显微捕获技术用于尿液脱落细胞DNA检测

目的采用激光显微捕获技术（LCM）捕获尿液脱落细胞,并进行STR分型。方法收集10份健康成人尿液样本,根据储存时间分组,其中新鲜尿液组（≤24h）分别采用Chelex-100及LCM联合DNA IQTM提取法提取DNA,储存尿液组（〉24h）再分为4℃组和室温组,分别在4～30d内不同时间点采用LCM联合DNA IQTM提取法提取DNA;各组提取的模板DNA进行扩增及SRT分型检验。结果新鲜尿液组采用LCM联合DNA IQTM提取法提取DNA,所有样本均可检出全部基因座（16个）,采用Chelex-100法则在部分基因座上出现等位基因丢失、非特异性扩增、峰值低等现象;4℃储存10d和室温储存4d以内的尿液经检验可明确判读12个以上基因座,4℃20～30d及室温7d,可检出7个以上基因座。结论 LCM技术可用于尿液检材的DNA分型检验,且检材应尽可能4℃保存并尽快检验。     

中国DNA数据库建设应用技术现状及发展趋势

中国的法庭科学DNA数据库建设历经10年,在应用中取得了显著成果.随着DNA分析技术的进步,DNA数据库更加完善,DNA信息作用更加突显.本文综述了中国DNA数据库的规划与建设,DNA数据库建设中的应用技术,以及DNA数据库建设应用技术发展趋势,为完善DNA数据库建设提供借鉴.