A PCR multiplex and database for forensic DNA identification of dogs

Animal-derived trace evidence is a common finding at crime scenes and may provide an important link between victim(s) and suspect(s). A database of 558 dogs of pure and mixed breeds is described and analyzed with two PCR multiplexes of 17 microsatellites. Summary statistics (number of alleles, expected and observed heterozygosity and power of exclusion) are compared between breeds. Marked population substructure in dog breeds indicates significant inbreeding, and the use of a conservative theta value is recommended in likelihood calculations for determining the significance of a DNA match. Evidence is presented that the informativeness of the canine microsatellites, despite inbreeding, is comparable to the human CODIS loci. Two cases utilizing canine DNA typing, State of Washington v. Kenneth Leuluaialii and George Tuilefano and Crown v. Daniel McGowan, illustrate the potential of canine microsatellite markers for forensic investigations.     

A proposal for standardization in forensic canine DNA typing: allele nomenclature of six canine-specific STR loci

In this study a proposal for the allele nomenclature of six polymorphic short tandem repeat (STR) loci (PEZ3, PEZ6, PEZ8, PEZ10, FHC2161, and FHC2328) for canine genotyping (Canis lupus familiaris) is presented. The nomenclature is based on the sequence data of the polymorphic region of the microsatellite markers as recommended by the DNA commission of the International Society of Forensic Haemogenetics (ISFH) in 1994 for human DNA typing. To cover commonly and rarely occurring alleles, a selection of homozygous and heterozygous animals were analyzed and subjected to sequence studies. The alleles consisted of simple tri- and tetra-nucleotide repeat patterns as well as compound and highly complex repeat patterns. Several alleles revealing the same fragment size but different repeat structures were found. The allele designation described here was adopted to the number of repeats, including all variable regions within the amplified fragment. In a second step the most commonly occurring alleles were added to an allelic ladder for each marker allowing a reliable typing of all alleles differing in size. A total number of 142 unrelated dogs from surrounding municipal animal homes, private households, and canines in police duty were analyzed. The data were added to a population database providing allele frequencies for each marker.     

荧光复合扩增4个Y染色体STR的单倍型及其法医学应用

目的建立一套Y染色体STR的双色荧光复合扩增系统,调查4个Y-STR基因座单倍型分布情况及其在混合斑物证检验中的法医学应用前景。方法荧光标记引物复合扩增Y-GATA-A10、DYS531、DYS557和DYS448四个Y染色体特异性STR基因座,并用ABⅠ310遗传分析仪对扩增产物进行检测、分型。结果在成都汉族120名无关男性个体中,四个基因座分别检出5、5、8、7个等位基因,共检出78种单倍型,单倍型基因多样性为0.9881。对3例本教研室不能用常规常染色体STR对男性成份作出同一认定的混合斑检材,该系统成功的作出了与嫌疑人血液Y-STR基因型一致的鉴定结论。结论建立的Y-STR荧光标记复合扩增系统具有很高的识别能力,对建立Y染色体STR数据库,研究群体遗传学和进行法医学混合斑物证鉴定有重要意义。     

复合扩增D16S539、D7S820、D13S317基因座的DNA分型及法医学应用

通过对3个位于不同染色体上的STR基因座（D165539,D7S820,D13S317）所组成的复合扩增体系的DNA分型研究,以期在实际法医物证检验中增加检验基因座,以提高总的个体识别率。笔者运用复合扩增技术,经4％变性聚丙烯酸胺凝胶电泳分离扩增产物和银染检测,首次对108个无关中国人个体的D16S539,D7S820,D13S317基因座进行研究,检测出中国人群中3个基因座的等位基因数均为7个;偶合率P（m）分别为0．0847、0．0740、0．0741;个体识别率DP值分别为0．9153、0．9260、0．9259;杂合度分别为77．7％、79.1％、79．3％;各基因座亲子关系指数PItypical分别为2．24、2．39、2．42。3个STR基因座总的个体识别率很高,达0．9995;总的亲子关系指数PItypical达12．96;所有基因座经卡方检验符合Hardy－Weinberg平衡。通过以上数据可以看出,D165539,D7S820,D13S317基因座所组成的复合扩增体系在中国人群中等位基因分布较好,个体识别率很高,适合用于法医个体识别及亲子鉴定。     

Genotyping for DQA1 and PM loci in urine using PCR-based amplification: effects of sample volume, storage temperature, preservatives, and aging on DNA extraction and typing.

Urine is often the sample of choice for drug screening in aviation/general forensic toxicology and in workplace drug testing. In some instances, the origin of the submitted samples may be challenged because of the medicolegal and socioeconomic consequences of a positive drug test. Methods for individualization of biological samples have reached a new boundary with the application of the polymerase chain reaction (PCR) in DNA profiling, but a successful characterization of the urine specimens depends on the quantity and quality of DNA present in the samples. Therefore, the present study investigated the influence of storage conditions, sample volume, concentration modes, extraction procedures, and chemical preservations on the quantity of DNA recovered, as well as the success rate of PCR-based genotyping for DQA1 and PM loci in urine. Urine specimens from male and female volunteers were divided and stored at various temperatures for up to 30 days. The results suggested that sample purification by dialfiltration, using 3000-100,000 molecular weight cut-off filters, did not enhance DNA recovery and typing rate as compared with simple centrifugation procedures. Extraction of urinary DNA by the organic method and by the resin method gave comparable typing results. Larger sample volume yielded a higher amount of DNA, but the typing rates were not affected for sample volumes between 1 and 5 ml. The quantifiable amounts of DNA present were found to be greater in female (14-200 ng/ml) than in male (4-60 ng/ml) samples and decreased with the elapsed time under both room temperature (RT) and frozen storage. Typing of the male samples also demonstrated that RT storage samples produced significantly higher success rates than that of frozen samples, while there was only marginal difference in the DNA typing rates among the conditions tested using female samples. Successful assignment of DQA1 + PM genotype was achieved for all samples of fresh urine, independent of gender, starting sample volume, or concentration method. Preservation by 0.25% sodium azide was acceptable for sample storage at 4 degrees C during a period of 30 days. For longer storage duration, freezing at -70 degrees C may be more appropriate. Thus, the applicability of the DQA1 + PM typing was clearly demonstrated for individualization of urine samples.     

Fingerprints and DNA: STR typing of DNA extracted from adhesive tape after processing for fingerprints

An exhibit that is often received for examination in cases of robbery or terrorist activity is adhesive tape. This type of exhibit can often, but not always, be successfully processed for fingerprints. The question arises whether or not it is possible to extract and type DNA after the tape has been sequentially processed for fingerprints. In this work, various donors left fingerprints on the adhesive side of tapes. The tapes were then sequentially processed for fingerprints using an alternate light source, cyanoacrylate fuming, and staining with BY-40 and then crystal violet. DNA was subsequently successfully extracted, amplified and typed for six STR loci.     

Development and validation of the AmpFlSTR MiniFiler PCR Amplification Kit: a MiniSTR multiplex for the analysis of degraded and/or PCR inhibited DNA

DNA typing of degraded DNA samples can be a challenging task when using the current commercially available multiplex short tandem repeat (STR) analysis kits. However, the ability to type degraded DNA specimens improves by redesigning current STR marker amplicons such that smaller sized polymerase chain reaction (PCR) products are generated. In an effort to increase the amount of information derived from these types of DNA samples, the AmpFlSTR MiniFiler PCR Amplification Kit has been developed. The kit contains reagents for the amplification of eight miniSTRs which are the largest sized loci in the AmpFlSTR Identifiler PCR Amplification Kit (D7S820, D13S317, D16S539, D21S11, D2S1338, D18S51, CSF1PO, and FGA). Five of these STR loci (D16S539, D21S11, D2S1338, D18S51, and FGA) also are some of the largest loci in the AmpFlSTR SGM Plus kit. This informative nine-locus multiplex, which includes the gender-identification locus Amelogenin, has been validated according to the FBI/National Standards and SWGDAM guidelines. Our results demonstrate significant performance improvements in models of DNA degradation, PCR inhibition, and nonprobative samples when compared to the AmpFlSTR Identifiler and SGM Plus kits. These data support that the MiniFiler kit will increase the likelihood of obtaining additional STR information from forensic samples in situations in which standard STR chemistries fail to produce complete profiles.     

Development of a one-tube extraction and amplification method for DNA analysis of sperm and epithelial cells recovered from forensic samples by laser microdissection

Laser microdissection can be used in forensic casework to isolate specific cell types from mixtures of biological samples. Extraction of DNA from selected cells is still required prior to STR amplification. Because of the relatively pristine nature of the recovered cells, laser microdissection is more sensitive than more traditional methods of DNA analysis, theoretically resulting in DNA profiles from less cellular material. A one-tube extraction and amplification method minimises loss of DNA through liquid transfers and reduces the potential for contamination events occurring. In this paper, the development of a one-tube method for the effective extraction of DNA from laser microdissected sperm and epithelial cells is described. The performance of the in-house method was compared to that of a commercial DNA extraction kit for extraction of DNA from sperm and the downstream compatibility with STR amplification was determined for both sperm and epithelial samples. Full Identifiler™ profiles after 28 amplification cycles were obtained from as few as 15 epithelial cells and 30 sperm.     

DNA typing of samples for polymarker, DQA1, and nine STR loci from a human body exhumed after 27 years

A body was exhumed from the ground after 27 years. Samples of femur bone, tooth, and a fingernail were collected and successfully subjected to DNA extraction, quantitation, amplification, and subsequently typed for DQA1, polymarker, and nine STR loci. All three types of samples were typed for D3S1358, vWA, FGA, D8S1179, D21S11, D18S51, D5S818, D13S17, D7S820, and amelogenin using ABI Prism 377 DNA sequencer.     

Development of an instrument for assessing the quality of forensic evidence and expert testimony from three feature-comparison methods: DNA,voice, and fingerprint analysis

In a context of rising violence and long-lasting impunity, in 2008, Mexico's criminal justice system underwent a radical change from an inquisitorial model to an adversarial one, to make it more effective, transparent, and expeditious. The new system tasked judges with publicly determining the admissibility of forensic evidence, as well as assessing its technical quality and probative value—tasks for which they currently receive little to no training. With the aim of contributing to the consolidation of the adversarial model, a comparative framework—in the form of a checklist—of the analysis of fingerprints, DNA samples, and voice recordings was created. To do so, a review of the academic literature, published reports, and guidelines was performed. The collected data were synthesized and submitted to a panel of Mexican judges, who provided feedback on its adequacy. The framework focuses on the steps on which quality assurance of forensic evidence depends, organized in five discrete stages that span from the collection of samples at the scene of a crime to the presentation of evidence at trial, specifying the main technical criteria experts should state to allow a decision maker to examine its accuracy and reliability. Differences and commonalities among the three methods were identified, particularly in terms of how qualitative and quantitative analyses are performed in each. Besides its potential usefulness as an aid for judicial decision-making, the checklist could be a valuable resource for training programs aimed at judges, as well as quality assurance programs.