Forensic application of DNA 'fingerprints'

Many highly polymorphic minisatellite loci can be detected simultaneously in the human genome by hybridization to probes consisting of tandem repeats of the 'core' sequence. The resulting DNA fingerprints produced by Southern blot hybridization are comprised of multiple hypervariable DNA fragments, show somatic and germline stability and are completely specific to an individual. We now show that this technique can be used for forensic purposes; DNA of high relative molecular mass (Mr) can be isolated from 4-yr-old bloodstains and semen stains made on cotton cloth and digested to produce DNA fingerprints suitable for individual identification. Further, sperm nuclei can be separated from vaginal cellular debris, obtained from semen-contaminated vaginal swabs, enabling positive identification of the male donor/suspect. It is envisaged that DNA fingerprinting will revolutionize forensic biology particularly with regard to the identification of rape suspects.     

Positive identification of an immigration test-case using human DNA fingerprints

The human genome contains a set of minisatellites, each of which consists of tandem repeats of a DNA segment containing the 'core' sequence, a putative recombination signal in human DNA. Multiallelic variation in the number of tandem repeats occurs at many of these minisatellite loci. Hybridization probes consisting of tandem repeats of the core sequence detect many hypervariable minisatellites simultaneously in human DNA, to produce a DNA fingerprint that is completely individual-specific and shows somatic and germline stability. These DNA fingerprints are derived from a large number of highly informative dispersed autosomal loci and are suitable for linkage analysis in man, and for individual identification in, for example, forensic science and paternity testing. They can also be used to resolve immigration disputes arising from lack of proof of family relationships. To illustrate the potential for positive or inclusive identification, we now describe the DNA fingerprint analysis of an immigration case, the resolution of which would have been very difficult and laborious using currently available single-locus genetic markers.     

DNA分子技术与鱼类种质资源研究

DNA分子技术为生物种内和种间的比较及遗传多样性提供了一种崭新而又行之有效的途径。简要介绍了Southerm杂交、RFLP、PCR、小卫星和微卫星技术、RAPD、原位PCR和DNA测序等几种DNA分子技术及其在鱼类种质资源研究中的应用情况。概述了我国分子水平上的鱼类种质资源研究现状和进展。     

分子标记技术及其应用

介绍了DNA分子标记的分类以及限制性片段长度多态性、小卫星 (minisatellite)DNA标记、微卫星(microsatellite)DNA标记技术、随机扩增多态性DNA(RAPD)、扩增片段长度多态性 (AFLP)和单核苷酸多态性等主要DNA分子标记的基本原理、优缺点以及它们在人类、动物等研究中的应用概况和展望。     

Demographic study of a wild house sparrow population by DNA fingerprinting

Over the past twenty years, several techniques from biochemical and molecular genetics, such as enzyme electrophoresis and isoelectric focusing, have been widely and successfully applied to the study of population differentiation and evolution. However, they have been less applicable to demographic problems such as assigning parentage to individuals within a population. This stems from a general weakness of data derived from enzyme loci: allele frequencies at polymorphic loci are sufficiently skewed that the majority of individuals are of one or two genotypes. Many enzyme systems can only be examined post mortem, so that the loci are of little use if the animals are to be studied in the wild. The search for new and more sensitive techniques for detecting genetic variation has continued, and recently a major discovery has come from molecular biology. Jeffreys et al. have reported the detection of a type of hypervariable 'minisatellite' DNA that is extraordinarily polymorphic in human populations. We have applied their technique to several bird species and particularly to a population of house sparrows (Passer domesticus) near Nottingham. We report here that one of the human minisatellite clones is a suitable probe for sparrow DNA and that it reveals variation as extensive as that found in man. These results suggest that analysis of minisatellite DNA will be a powerful tool in the study of demographic population genetics.     

Spontaneous mutation rates to new length alleles at tandem-repetitive hypervariable loci in human DNA

Tandem-repetitive minisatellite regions in vertebrate DNA frequently show substantial allelic variation in the number of repeat units. This variation is thought to arise through processes such as unequal crossover or replication slippage. We show here that the spontaneous mutation rate to new length alleles at extremely variable human minisatellites is sufficiently high to be directly measurable in human pedigrees. The mutation rate at different loci increases with variability in accord with the neutral mutation/random drift hypothesis, and rises to 5% per gamete for the most unstable human minisatellite isolated. Mutations are sporadic, occur with similar frequencies in sperm and oocytes, and can involve the gain or loss of substantial numbers of repeat units, consistent with length changes arising primarily by unequal exchange at meiosis. Germline instability must therefore be taken into account when using hypervariable loci as genetic markers, particularly in pedigree analysis and parenthood testing.     

DNA typing from single hairs

The characterization of genetic variation at the DNA level has generated significant advances in gene and disease mapping, and in the forensic identification of individuals. The most common method of DNA analysis, that of restriction fragment length polymorphism (RFLP), requires microgram amounts of relatively undegraded DNA for multi-locus typing, and hundreds of nanograms for single-locus comparisons. Such DNA frequently cannot be obtained from forensic samples such as single hairs and blood stains, or from anthropological, genetic or zoological samples collected in the field. To detect polymorphic DNA sequences from single human hairs, we have used the polymerase chain reaction (PCR), in which specific short regions of a gene can be greatly amplified in vitro from as little as a single molecule of DNA. We have detected genetically variable mitochondrial and nuclear DNA sequences from the root region of shed, as well as freshly-plucked, single hairs; mitochondrial DNA (mtDNA) sequences have been detected in a sample from a single hair shaft. We have used three different means of DNA typing on these samples: the determination of amplified DNA fragment length differences, hybridization with allele-specific oligonucleotide probes, and direct DNA sequencing.     

DNA宏条形码技术在动植物法医鉴定中的应用进展

DNA宏条形码技术是随着2代高通量测序技术的发展而出现的一种物种鉴别技术.该技术结合了DNA条形码技术和高通量测序技术的优点,可以对混合样本中的多物种来源进行同步鉴定.本研究介绍DNA宏条形码技术的含义以及目前的应用需求,分析DNA宏条形码技术在食品、药品监管、打击野生动植物犯罪、刑事案件侦查等司法实践中的应用现状,总...     

Hypervariable 'minisatellite' regions in human DNA

The human genome contains many dispersed tandem-repetitive 'minisatellite' regions detected via a shared 10-15-base pair 'core' sequence similar to the generalized recombination signal (chi) of Escherichia coli. Many minisatellites are highly polymorphic due to allelic variation in repeat copy number in the minisatellite. A probe based on a tandem-repeat of the core sequence can detect many highly variable loci simultaneously and can provide an individual-specific DNA 'fingerprint' of general use in human genetic analysis.     

Identification of the skeletal remains of a murder victim by DNA analysis

There is considerable anthropological and forensic interest in the possibility of DNA typing skeletal remains. Trace amounts of DNA can be recovered even from 5,500-year-old bones and multicopy human mitochondrial DNA sequences can frequently be amplified from such DNA using the polymerase chain reaction (PCR). But given the sensitivity of PCR, it is very difficult to exclude contaminating material. We now report the successful identification of the 8-year-old skeletal remains of a murder victim, by comparative typing of nuclear microsatellite markers in the remains and in the presumptive parents of the victim. This analysis establishes the authenticity of the bone DNA and the feasibility of bone DNA typing in forensic investigations.     

Individual-specific 'fingerprints' of human DNA

Simple tandem-repetitive regions of DNA (or 'minisatellites') which are dispersed in the human genome frequently show substantial length polymorphism arising from unequal exchanges which alter the number of short tandem repeats in a minisatellite. We have shown previously that the repeat elements in a subset of human minisatellites share a common 10-15-base-pair (bp) 'core' sequence which might act as a recombination signal in the generation of these hypervariable regions. A hybridization probe consisting of the core repeated in tandem can detect many highly polymorphic minisatellites simultaneously to provide a set of genetic markers of general use in human linkage analysis. We now show that other variant (core)n probes can detect additional sets of hypervariable minisatellites to produce somatically stable DNA 'fingerprints' which are completely specific to an individual (or to his or her identical twin) and can be applied directly to problems of human identification, including parenthood testing.     

混合斑的DNA鉴定的几种方法研究

在法医物证学上,对于混合斑检材,通常采用Chelex法提取DNA后扩增再查看相关位点。在实际运用中,该法存在很大不足。为了提高鉴定成功率,作者对现有混合斑DNA鉴定的几种方法进行综合比较研究,现总结如下。     

Evaluating the reliability of microsatellite genotyping from low-quality DNA templates with a polynomial distribution model

Molecular studies using trace DNA, such as from museum specimens, ancient or forensic samples and samples obtained noninvasively, often have a common problem of low quality of DNA templates. Amplification errors, such as allelic dropout and false allele, may arise during polymerase chain reaction (PCR) using such samples. A mathematical model which treats homozygotes and heterozygotes discriminately has been developed to measure sample quality and compute the confidence level of using multipletube approaches. We use plucked hair samples collected from 26 individual Sichuan snub-nosed monkeys (Rhinopithecus roxel- lana) to test the model. In this case, a confidence level of 99% can be achieved by three positive PCRs. If the sample quality is very poor and requires many PCR replicates, an alternative multiplestep genotyping method is recommended. This model enables researchers to optimize experimental protocols through pilot studies and obtain reliable genetic information using noninvasive sampling method.     

Genetic fingerprinting reflects population differentiation in the California Channel Island fox

Restriction fragment profiles generated by hybridization of hypervariable minisatellite DNA probes have been used for paternity analysis but not for comparisons at the level of populations, because the profiles are thought to evolve too rapidly to be informative over large time intervals. But in small isolated populations, the fixation of restriction-fragment polymorphisms can outpace the generation of fragment-length variability through recombination. Here we report on an analysis of DNA fingerprints of the California Channel Island fox (Urocyon littoralis). These foxes comprise an island dwarf species found only on six of the Channel Islands off the coast of southern California. Variability of restriction-fragment profiles within fox populations, as indicated by the average percentage difference (APD), varied widely among the islands, from 0.0% (no variation) to 25.3%. The APDs between populations were considerably greater (43.8% to 84.4%). In addition, foxes on each island can be distinguished by the presence of diagnostic restriction fragments. Maximum parsimony and phenetic trees relating foxes from different islands are consistent with the archaeozoological and geological record. Therefore, in small populations of genetically isolated mammals, differences among hypervariable restriction-fragment profiles can be used to estimate relative genetic variability and to reconstruct the evolutionary relationships of natural populations.     

No evidence for illegitimate young in monogamous and polygynous warblers

In animals with internal fertilization, paternity is uncertain. In birds, the occurrence of copulations outside the pair-bond has been documented in a number of species, but the extent to which these result in illegitimate young is largely unknown, and constitutes a major deficiency in our understanding of avian mating systems. The analysis of tandemly repeated sequences (minisatellites), has enhanced our ability to make individual identifications and paternity determinations. Here we describe the use of a bird minisatellite DNA probe in assigning paternity in natural populations of the monogamous willow warbler Phylloscopus trochilus and of the polygynous wood warbler Phylloscopus sibilatrix. In both species this probe detects a multiple locus pattern and a single locus that exhibits a variable number of tandem repeats. Although we observed intrusions by non-resident males into the territories of paired males and extra-pair copulations, no illegitimate offspring were detected among 176 young from 32 families of both species, implying that extra-pair copulations have little or no genetic impact.     

Genes mirror geography within Europe

Understanding the genetic structure of human populations is of fundamental interest to medical, forensic and anthropological sciences. Advances in high-throughput genotyping technology have markedly improved our understanding of global patterns of human genetic variation and suggest the potential to use large samples to uncover variation among closely spaced populations. Here we characterize genetic variation in a sample of 3,000 European individuals genotyped at over half a million variable DNA sites in the human genome. Despite low average levels of genetic differentiation among Europeans, we find a close correspondence between genetic and geographic distances; indeed, a geographical map of Europe arises naturally as an efficient two-dimensional summary of genetic variation in Europeans. The results emphasize that when mapping the genetic basis of a disease phenotype, spurious associations can arise if genetic structure is not properly accounted for. In addition, the results are relevant to the prospects of genetic ancestry testing; an individual's DNA can be used to infer their geographic origin with surprising accuracy-often to within a few hundred kilometres.     

智能取证技术研究

计算机取证已成为解决争议和打击计算机犯罪的重要手段,充分利用智能信息处理技术实现计算机取证的意义重大。从取证形式化分析、用户行为分析、智能图像取证、智能视频取证4个方面讨论了近年来智能取证技术的发展及其存在的问题,最后对智能取证技术未来趋势作了分析讨论。     

浅谈影响司法鉴定质量的原因与对策

司法鉴定结论对于准确的定罪量刑,保证办案质量,避免冤假错案有着十分重要的作用。然而,目前在我国司法鉴定实践中,司法鉴定机构设置、鉴定标准、制度建设、鉴定人素质等方面还存在一些不足,致使鉴定结论的科学性、客观性、公正性受到了一定程度的影响。应建立统一合理的司法鉴定制度,规范统一的鉴定标准,建立鉴定机构和鉴定人的资质认证和社会评价制度,规范鉴定结论的质证机制,从而提高司法鉴定质量。     

计算机取证综述

随着网络技术的发展,计算机犯罪不断增加。为了打击高科技犯罪,取证技术作为计算机科学与法学之间的交叉学科,成为当今社会必不可少的一部分。研究了取证科学的产生和发展,分析了取证基本原则,重点总结了几种典型的取证模型和取证工具,有利于对取证过程的正确分析和理解。     

A forensic method for efficient file extraction in HDFS based on three-level mapping

The large scale and distribution of cloud computing storage have become the major challenges in cloud forensics for file extraction. Current disk forensic methods do not adapt to cloud computing well and the forensic research on distributed file system is inadequate. To address the forensic problems, this paper uses the Hadoop distributed file system (HDFS) as a case study and proposes a forensic method for efficient file extraction based on three-level (3L) mapping. First, HDFS is analyzed from overall architecture to local file system. Second, the 3L mapping of an HDFS file from HDFS namespace to data blocks on local file system is established and a recovery method for deleted files based on 3L mapping is presented. Third, a multi-node Hadoop framework via Xen virtualization platform is set up to test the performance of the method. The results indicate that the proposed method could succeed in efficient location of large files stored across data nodes, make selective image of disk data and get high recovery rate of deleted files.