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PubMed1994

Greater differences in forensic DNA profile frequencies estimated from racial groups than from ethnic subgroups.

A National Research Council (NRC) report asserted that genetic diversity between subgroups within a race is greater than between races. While this is counterintuitive to the basic tenets of human population genetics, the forensic application of statistical estimates of DNA profile frequencies has been questioned. The general approach used for estimating DNA profile frequencies by the majority of North American forensic laboratories is the use of the product rule on fixed bin allele frequencies derived from general population group databases. An informal analysis of the differences in frequency estimates within Hinf I-generated RFLP data determined in three ethnically distinct population groups--Norwegians, Spanish, and Turks--and in Caucasians and Blacks from the United States is presented. The VNTR loci analyzed are D2S44, D7S21, and D12S11. The data demonstrate that the assertion by the NRC is unfounded and that major population group databases, in lieu of subpopulation databases, can be used to provide estimates of DNA profile frequencies without consequences of wrongful bias.

Black People↗

PubMed1996

Sequence variation of a hypervariable short tandem repeat at the D12S391 locus.

A short tandem repeat (STR) in the D12S391 locus was sequenced in more than 40 individuals. Twenty different alleles were found and these could be grouped into 12 allelic classes in accordance with the total number of repeats. This is a compound STR consisting of blocks of (AGAT) and (AGAC) repeats with basic sequence structure (AGAT)8-17(AGAC)6-10(AGAT)0-1. Whereas smaller alleles (15-18) have variation limited to the (AGAT) unit, in larger alleles the complexity is greater with variation in the number of tandem arrays in the two motifs (AGAT) and (AGAC). Population data showed that this is a highly polymorphic STR with a heterozygosity of more than 0.9. This fact, together with its simple structure, makes this STR an interesting DNA polymorphism for forensic and genetic purposes.

Alleles↗

PubMed2006

[Polymorphisms of seven short tandem repeat loci: D1S2142, D1S3733, D2S1774, D3S2459, D21S1409, D21S1437 and D21S2055 of Chinese Han population in Chengdu].

OBJECTIVE: To obtain the data in polymorphism distribution of the seven short tandem repeat (STR) loci: D1S2142, D1S3733, D2S1774, D3S2459, D21S1409, D21S1437 and D21S2055 of Chinese Han population in Chengdu, and evaluate the polymorphism data usefulness to the forensic science. METHODS: PCR, polyacrylamide gel electrophoresis (PAGE) and silver staining techniques were used to analyze the DNA samples from unrelated individuals of Chinese Han ethnic group in Chengdu. RESULTS: Eleven alleles and twenty-three genotypes were observed in D1S2142. Eight alleles and nineteen genotypes were observed in D1S3733. Eight alleles and fifteen genotypes were observed in D2S1774. Seven alleles and nineteen genotypes were observed in D3S2459. Six alleles and twelve genotypes were observed in D21S1409. Nine alleles and twenty-six genotypes were observed in D21S1437. Twenty alleles and seventy-seven genotypes were observed in D21S2055. The genotype distributions of the seven STR loci showed no deviation from the Hardy-Weinberg equilibrium. The parentage testing of 50 cases revealed an autosomal codominant inheritances and no mutations happened to seven STR loci. CONCLUSION: These data indicate that D1S2142, D1S3733, D2S1774, D3S2459, D21S1409, D21S1437 and D21S2055 have good polymorphism, with high probability of exclusion and probability of discrimination power as well as being loci available as the candidate genetic markers to forensic parentage testing and personal identification.

Alleles↗

PubMed2004

Encoded evidence: DNA in forensic analysis.

Sherlock Holmes said "it has long been an axiom of mine that the little things are infinitely the most important", but never imagined that such a little thing, the DNA molecule, could become perhaps the most powerful single tool in the multifaceted fight against crime. Twenty years after the development of DNA fingerprinting, forensic DNA analysis is key to the conviction or exoneration of suspects and the identification of victims of crimes, accidents and disasters, driving the development of innovative methods in molecular genetics, statistics and the use of massive intelligence databases.

DNA Fingerprinting↗

PubMed2005

[Applications of DNA methylation markers in forensic medicine].

DNA methylation is a post-replication modification that is predominantly found in cytosines of the dinucleotide sequence CpG. Epigenetic information is stored in the distribution of the modified base 5-methylcytosine. DNA methylation profiles represent a more chemically and biologically stable source of molecular diagnostic information than RNA or most proteins. Recent advances attest to the great promise of DNA methylation markers as powerful future tools in the clinic. In the past decade, DNA methylation analysis has been revolutionized by two technological advances--bisulphite modification of DNA and methylation-specific polymerase chain reaction (MSP). The methylation pattern of human genome is space-time specific, sex-specific, parent-of-origin specific and disease specific, providing us an alternative way to solve forensic problems.

Base Sequence↗

PubMed2005

Forensic assessment of 16 single nucleotide polymorphisms analyzed by hybridization probe assay.

Of a number of DNA marker typing techniques for personal identification in the field of forensic medicine, polymorphic short tandem repeat (STR) typing is currently the most frequently used technique. However, the multiplex STR method is time consuming. In contrast, single nucleotide polymorphism (SNP) detection methods are relatively rapid and amenable to high throughput. The discrimination power of each SNP is inferior to that of an STR, but a combination of many SNPs could realize a high discriminating power. In this regard, 16 highly informative SNP markers were selected in the introns of genes whose alleles had a proportion of 0.4-0.6 in the Japanese SNP database. The 16 SNPs were sequentially detected within 40 min using the hybridization probe assay on the LightCycler system. The allele and genotype frequencies of these SNPs were determined in a group comprising 64 unrelated Japanese subjects. Based on the frequency data of this group, the combined matching probability, defined as the estimated probability that two unrelated individuals selected at random would possess identical multilocus genotypes, was calculated with the 16 SNPs in the Japanese population and was found to be 2.025x10(-7). This system is an effective tool in the forensic medicine to obtain information on personal identification.

Alleles↗

PubMed2005

[The forensic applications of sex chromosomes and mtDNA genetic markers].

This article summarizes the structure and heredity characteristics of sex chromosomes and mtDNA, presents the advantages and disadvantages of genetic markers' on them in the practice of forensic medicine which aims at promoting more widely using of the non-euchromosome DNA genetic markers in the forensic science.

Chromosomes, Human, X↗

PubMed2006

[Genetic polymorphisms of three loci and implication to forensic medicine].

OBJECTIVE: To obtain population genetic data of short tandem repeat (STR) locus D2S1327, D1S1390, and D11S2008 and to investigate the disparity of allelic frequency distributions among populations from different regions. METHODS: Blood samples of 300 unrelated individuals from Chengdu (Han), Bangkok (Thai) and Maint (Germany) were taken and analyzed with single PCR, polyacrylamide gel electrophoresis and silver staining. RESULTS: In the three loci, 9, 6, and 8 alleles and 32,14, and 22 genotypes were found respectively. The observed heterozygosity of 79%-82%, 63.0%-74.3%, and 72.0%-74.3% and discrimination power of 87.8%-92.6%, 79.6%-82.5%, and 87.6%-89.0% were identified for the three loci respectively. The genotype distributions of the three loci in the three populations fitted well with Hardy-Weinberg equilibrium. There was no significant difference in allelic frequency distributions among the three populations. CONCLUSION: The methods described in this paper are easy to perform and have high sensitivities. The discrimination power and exclusion chances of these three loci are desirable for forensic analysis and application.

China↗

PubMed2006

Effects of coancestry on accuracy of individual assignments to population of origin: examples using Great Lakes lake trout (Salvelinus namaycush).

Methods for assigning individuals to population of origin are widely used in ecological genetics, resources management, and forensics. Characteristics of genetic data obtained from putative source populations that enhance accuracy of assignment are well established. How non-independence within and among unknown individuals to be classified [i.e., gene correlations within individual (inbreeding) and gene correlations among individuals within group (coancestry)] affect assignment accuracy is poorly understood. We used empirical data for six microsatellite loci and offspring from full-sib crosses of hatchery strains of lake trout (Salvelinus namaycush; Salmonidae) representing known levels of coancestry (mean theta = 0.006 and 0.06) within families to investigate how gene correlations can affect assignment. Additional simulations were conducted to further investigating the influence of allelic diversity (2, 6 or 10 alleles per locus) and inbreeding (F = 0.00, 0.05, and 0.15) on assignment accuracy for cases of low and high inter-population variance in allele frequency (mean F (st) = 0.01 and 0.1, respectively). Inbreeding had no effect on accuracy of assignments. In contrast, variance in assignment accuracy across replicated simulations, and for each empirical case study increased with increasing coancestry, reflecting non-independence of probabilities of correct assignment among members of kin groups. Empirical estimates of assignment error rates should be interpreted with caution if appreciable levels of coancestry are suspected. Additional emphasis should be placed on sampling designs (spatially and temporally) that define or minimize the potential for sampling related individuals.

Animal Population Groups↗

PubMed2000

Identification of the human Y-chromosomal microsatellite locus DYS19 from degraded DNA.

STR DYS19 seems to be one of the most useful markers for population genetic, evolutionary, and forensic applications. However, the authors have noticed that the amplification of the DYS19 polymorphism fails when highly degraded DNA is used as a template. The authors designed a new pair of primers that reduce the DYS19 fragment sizes compared with those of the known protocol. Using these primers, an improved success rate can be achieved, particularly when putrefied samples are under investigation.

Alleles↗

PubMed2006

[Genetic polymorphisms and application of 9 STR loci of 5 ethnic groups in Gansu and Qinghai].

OBJECTIVE: To examine the genetic polymorphism of 9 STR loci in 5 ethnic groups (including Tu, Sala, Dongxiang, Baoan and Yugu) in Gansu and Qinghai, and to evaluate its application. METHODS: Nine STR loci (D3S1358, FGA, TH01, D7S820, VWA, CSF1PO, D5S818, D13S317 and TPOX) were selected as genetic markers. With STR compound amplification and genescan methods, in which STR loci were marked by fluorescence, the genotype of 5 ethnic groups were examined in 606 unrelated individuals by ABI 377 sequencer. These parameters, such as polymorphism information content (PIC), heterozygosity (H), discrimination power (DP) and probability of paternity exclusion (PPE) were calculated. RESULTS: The genotype frequencies of the 9 STR loci were in accordance with Hardy-Weinberg equilibrium. PIC was within 0.6054 - 0.8735, H was within 0.6158 - 0.8736, DP was within 0.7964 - 0.9691, and PPE was within 0.4610 - 0.8838. Cluster analysis based on allele frequencies in genesis showed Tu, Sala, Dongxiang and Baoan ethnic groups were very close, but Yugu was a little bit far. There were obvious gene exchanges among the populations in north and south of China. CONCLUSION: All the 9 STR loci are highly polymorphic in the 5 ethnic groups, which can be useful genetic markers in forensic medicine and population genetics.

China↗

PubMed1991

Identification of individuals with DNA testing.

The fast technical development in molecular biology and the increasing knowledge of the human genome has had a major impact on forensic medicine. Genetic characterization of individuals at the DNA level enables identity testing from a minimal amount of biological specimen in cases of sexual assault, homicide, and unknown human remains. Also paternity testing is changing from level of gene products to the genomic level. This article addresses some of the advantages of DNA testing over the conventional forensic serology, and the DNA techniques currently used in forensic science.

ABO Blood-Group System↗

PubMed2005

HIV legal precedent useful for microbial forensics.

The field of microbial forensics was formalized because of the need for attribution in events where a bioweapon has been used. Microbial forensics has its origins in traditional forensics, microbiology, and epidemiology. Microbial forensics can be defined as a scientific discipline dedicated to analyzing evidence for attribution purposes from a bioterrorism act, biocrime, hoax, or inadvertent microorganism/toxin release. This is a very challenging task, since there are myriad microorganisms that can pose a threat, and analytical methods need to be used reliably. The Scientific Working Group on Microbial Genetics and Forensics (SWGMGF) has addressed some quality assurance and control issues, and particularly validation criteria (focusing on preliminary validation) due to the dynamic nature of evolving investigations. Unique identification of a microorganism may never be possible. Yet, qualitative and/or quantitative assessments of the evidence can be made. One approach to provide direction on gaps in the microbial forensics effort is to perform an end-to-end retrospective analysis of past cases. As an example, the case of a gastroenterologist who was accused of second degree attempted murder of his paramour using HIV as the weapon was reviewed. The scientific evaluation involves epidemiology, molecular biology, phylogenetics, and legal deliberations.

Bioterrorism↗

PubMedDate not supplied

[Research of potentially linked variation of polymorphism of chromosome DNA in aspect of forensic expertise using molecular-genetic individualizing systems CD4, vWA and vWFII].

Investigated within the case study are parameters of disbalance of lineage (HC) for 4 micro-satellite locuses of human genome: LPL, CD4, vWA and vWFII. The above locuses are widely used, both in Russia and abroad, in molecular-genetic applications for personality identification. Meanwhile, according to cytogenetics criteria, CD4, vWA and vWFII, are located close to each other in the telomeric region 12pter-12p12 in the short chromosome 12 arm, therefore their potential genetic interdependence is still a topical issue. We found a reliable HC between locuses vWA and vWFII. Locus CD4 did not display HC with locuses vWA and vWFII or with locus LPL. The latter, which is located in chromosome 8 and which must have been negative control for HC, was shown to have no HC with any of the studied markers. Such results correlate well with data on the relative physical localization of CD4, vWA, vWFII and LPL. Multiplication of frequency of alleles (genotypes) is not acceptable in typing locuses vWA and vWFII within one multi-locus panel due to the genetic linkage of these markers demonstrated within the present case study, which is an important practical conclusion.

Alleles↗

PubMed1996

Whole genome amplification using a degenerate oligonucleotide primer allows hundreds of genotypes to be performed on less than one nanogram of genomic DNA.

Genetic analysis of limiting quantities of genomic DNA play an important role in DNA forensics, paleoarcheology, genetic disease diagnosis, genetic linkage analysis, and genetic diversity studies. We have tested the ability of degenerate oligonucleotide primed polymerase chain reaction (DOP-PCR) to amplify picogram quantities of human genomic DNA for the purpose of increasing the amount of template for genotyping with microsatellite repeat markers. DNA was uniformly amplified at a large number of typable loci throughout the human genome with starting template DNAs from as little as 15 pg to as much as 400 ng. A much greater-fold enrichment was seen for the smaller genomic DOP-PCRs. All markers tested were amplified from starting genomic DNAs in the range of 0.6-40 ng with amplifications of 200- to 600-fold. The DOP-PCR-amplified genomic DNA was an excellent and reliable template for genotyping with microsatellites, which give distinct bands with no increase in stutter artifact on di-, tri-, and tetranucleotide repeats. There appears to be equal amplification of genomic DNA from 55 of 55 tested discrete microsatellites implying near complete coverage of the human genome. Thus, DOP-PCR appears to allow unbiased, hundreds-fold whole genome amplification of human genomic DNA for genotypic analysis.

DNA↗

PubMed1999

[Allele and genotype frequency distribution of D19S400 locus in several populations].

Using polymerase chain reaction and PAG electrophoresis, D19S400 Locus was investigated in the populations of Chinese, Germany, Slovakian, and American Black Population. 620 samples collected from the four populations were tested and a total of 11 alleles (*7 to *17) and 47 genotypes were found. The heterozygosity was observed between 0.78 and 0.88, and the discriminating power was between 0.9385 and 0.9664. The distributions of genotypes in the four populations were in accordance with Hardy-Weinberg equilibrium. Significant differences were observed in the distribution of allele frequencies among the three major racial populations (Mongoloid, Caucasian, Negroid). According to the results obtained in this study, D19S400 locus is a robust STR for forensic and genetic purposes.

Alleles↗

PubMed1997

Effects of subpopulation structure on probability calculations of DNA profiles from forensic PCR analysis.

DNA typing for forensic identification is a two-step process. The first step involves determining the profiles of samples collected at the crime scene and comparing them with the profiles obtained from suspects and the victims. In the case of a match that includes the suspect as the potential source of the material collected at the crime scene, the last step in the process is to answer the question, what is the likelihood that someone in addition to the suspect could match the profile of the sample studied? This likelihood is calculated by determining the frequency of the suspect's profile in the relevant population databases. The design of forensic databases and the criteria for comparison has been addressed by the NRC report of 1996 (National Research Council, 1996). However, the fact that geographical proximity, migrational patterns, and even cultural and social practices have effects on subpopulation structure establishes the grounds for further study into its effects on the calculation of probability of occurrence values. The issue becomes more relevant in the case of discrete polymorphic markers that show higher probability of occurrence in the reference populations, where several orders of magnitude difference between the databases may have an impact on the jury. In this study, we calculated G values for all possible pairwise comparisons of allelic frequencies in the different databases from the races or subpopulations examined. In addition, we analyzed a set of 24 unrelated Caucasian, 37 unrelated African-American, and 96 unrelated Sioux/Chippewa individuals for seven polymorphic loci (DQA1, LDLR, GYPA, HBGG, D7S8, GC, and D1S80). All three sets of individuals where sampled from Minnesota. The probability of occurrence for all seven loci were calculated with respect to nine different databases: Caucasian, Arabic, Korean, Sioux/Chippewa, Navajo, Pueblo, African American, Southeastern Hispanic, and Southwestern Hispanic. Analysis of the results demonstrated marked differences in the probabilities of occurrence when individuals were compared to the different populations and subpopulation databases. The possible genetic and forensic consequences of subpopulation structure on probability calculations are discussed.

DNA Fingerprinting↗

PubMedDate not supplied

Study of three hypervariable DNA loci (D1S7; D7S22 and D12S11) in three European populations.

To investigate the population genetic characteristics and genetic affinity, DNA profiles of three highly polymorphic VNTR (variable number of tandem repeats) loci (D1S7; D7S22 and D12S11) were studied in 405 individuals from three major European populations (English, Spanish and Basques). Like other studies on VNTRs, a large significant heterozygote deficiency was observed in all three populations. This decrease was ascribed to the limitation, coalescence and non-detectibility of alleles associated with the RFLP (restriction fragment length polymorphism) technique, through which the VNTR loci are genotyped. When the non-detectable alleles were taken into consideration, analyses of fragment sizes at these loci within each sample, as well as their fixed binned analyses, reveal that the assumptions of independence of allelelic occurrences within and between loci are valid for this European data. By comparing genetic variation at three VNTR loci with 17 blood groups, proteins and HLA loci in three well defined European populations, it is shown that the pattern of differentiation at these sets of loci are in general parallel especially for the hypervariable loci HLA and VNTR. Fixed-bin allele frequencies, therefore, are the best descriptions of such a database both for population genetic and forensic calculation studies. The Basques, with regard to VNTR loci, do not show any reduced genetic variability compared to other two European populations (English and Spanish).

Chromosome Mapping↗