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Forensic DNA databases.

Genetic databases have been created in several countries: the United Kingdom was the first European country to have, in 1995, a DNA database. Subsequently, the Netherlands and Austria (1997), Germany (1998), Finland and Norway (1999) and many others have introduced or are preparing databases. Different national legal systems have conditioned the DNA databases and so there is a great heterogeneity between countries. The criteria for an entry of a DNA profile, the criteria for a removal, the criteria for a search, etc., can lead to very distinct databases.

DNA Fingerprinting↗

Genetic relationships between blowflies (Calliphoridae) of forensic importance.

Phylogenetic relationships among blowfly (Calliphoridae) species of forensic importance are explored using DNA sequence data from the large sub-unit (lsu, 28S) ribosomal RNA (rRNA) gene, the study includes representatives of a range of calliphorid species commonly encountered in forensic analysis in Britain and Europe. The data presented provide a basis to define molecular markers, including the identification of highly informative intra-sequence regions, which may be of use in the identification of larvae for forensic entomology. Phylogenetic analysis of the sequences also provides new insights into the different evolutionary patterns apparent within the family Calliphoridae which, additionally, can provide a measure of the degree of genetic variation likely to be encountered within taxonomic groups of differing forensic utility.

Animals↗

Genetic analysis and attribution of microbial forensics evidence.

Because of the availability of pathogenic microorganisms and the relatively low cost of preparing and disseminating bioweapons, there is a continuing threat of biocrime and bioterrorism. Thus, enhanced capabilities are needed that enable the full and robust forensic exploitation and interpretation of microbial evidence from acts of bioterrorism or biocrimes. To respond to the need, greater resources and efforts are being applied to the burgeoning field of microbial forensics. Microbial forensics focuses on the characterization, analysis and interpretation of evidence for attributional purposes from a bioterrorism act, biocrime, hoax or inadvertent agent release. To enhance attribution capabilities, a major component of microbial forensics is the analysis of nucleic acids to associate or eliminate putative samples. The degree that attribution can be addressed depends on the context of the case, the available knowledge of the genetics, phylogeny, and ecology of the target microorganism, and technologies applied. The types of genetic markers and features that can impact statistical inferences of microbial forensic evidence include: single nucleotide polymorphisms, repetitive sequences, insertions and deletions, mobile elements, pathogenicity islands, virulence and resistance genes, house keeping genes, structural genes, whole genome sequences, asexual and sexual reproduction, horizontal gene transfer, conjugation, transduction, lysogeny, gene conversion, recombination, gene duplication, rearrangements, and mutational hotspots. Nucleic acid based typing technologies include: PCR, real-time PCR, MLST, MLVA, whole genome sequencing, and microarrays.

Bacterial Typing Techniques↗

The appropriate use of subpopulation corrections for differences in endogamous communities.

Zhivotovsky et al. [L.A. Zhivotovsky, S. Ahmed, W. Wang, A. Bittles, The forensic DNA implications of genetic differentiation between endogamous communities, Forensic Sci. Int. 119 (2001) 269-272] gave an estimate of 0.13 for the coancestry coefficient, theta in three co-resident Pakistani communities. Wang et al. [W. Wang, S.G. Sullivan, S. Ahmed, D. Chandler, L.A. Zhivotovsky, A.H. Bittles, A genome-based study of consanguinity in three co-resident endogamous Pakistan communities, Ann. Hum. Genet. 94 (2000) 41-49] explain that the sampling is from extended families but conclude that "the present findings show that differentiation resulting from genetic stratification by genetic relatedness can be very pronounced in specific populations and thus be important in the evaluation of forensic DNA evidence." In this paper we present simulation results that show that sampling from families will be expected to produce high values of theta regardless of the population value for theta. A theta value estimated in this way cannot be used in formulae suggested by NRC II [NRC II, National Research Council Committee on DNA Forensic Science, The Evaluation of Forensic DNA Evidence, National Academy Press, Washington, DC, 1996] (Eqs. (1) and (2)) to estimate the match probability for a DNA profile in a subpopulation. Whilst it may have some application to estimating the match probability from the pedigree itself there are superior methods for assigning match probabilities for relatives.

Asian People↗

[Genetic polymorphism of FIBRA,DHFRP2 and ACTBP2 and their forensic application in Yunnan Han population].

To investigate the genetic polymorphism of FIBRA,DHFRP2 and ACTBP2 in Yunnan Han population as well as their application in forensic science, EDTA-blood specimens were collected from 200 healthy individuals. The DNA were extracted either by the Chloro form, phenol method or by the Chelex-100 method. The PCR products were analyzed by PAG vertical electrophoresis,following by silver staining. All gene frequencies, discrimination power (DP), exclusion of paternity probability (EPP), heterozygosity (H),polymorphisms information content (PIC),matching probability (PM) as well as the Hardy-Weinberg test were calculated. The obtained data are beneficial in the understanding of population genetics of the three STR loci in Yunnan Han population and the results suggest that these loci are valuable genetic markers for paternity testing and personal identification in forensic science practice.

English Abstract↗

Genetic polymorphism of human alpha 2HS-glycoprotein: characterization and application to forensic hemogenetics.

Human alpha 2HS-glycoprotein (AHSG) phenotypes were studied by isoelectric focusing of native and desialyzed samples followed by passive immunoblotting. At present a total of 15 different alleles could be distinguished. The usefulness of AHSG polymorphism in the field of forensic hemogenetics was demonstrated by markedly high variability at AHSG locus, reliability of phenotyping results and stability in blood stains.

Alleles↗

The STR locus D11S554: allele frequencies and sequence data in a Japanese population.

A population study on the short tandem repeat (STR) locus D11S554 was carried out in a sample of 362 unrelated Japanese individuals living in the Gifu Prefecture. A total of 46 different alleles ranging from 180 bp to 340 bp and 135 genotypes were revealed. Sequence analysis of alleles was carried out for 185 samples. The sequence structures of the repeat regions of the alleles were found to be complex and the alleles were classified into nine sequence types, including four new sequence types. According to the system of Adams et al. (1993), we designated the new sequence types IA3, IA4, IA5 and IB3, respectively. Out of the 46 different alleles, 11 showed sequence heterogeneity. The results of this study demonstrated that the D11S554 locus is a powerful and useful genetic marker for forensic practice in the Japanese population.

Alleles↗

High direct estimate of the mutation rate in the mitochondrial genome of Caenorhabditis elegans.

Mutations in the mitochondrial genome have been implicated in numerous human genetic disorders and offer important data for phylogenetic, forensic, and population genetic studies. Using a long-term series of Caenorhabditis elegans mutation accumulation lines, we performed a wide-scale screen for mutations in the mitochondrial genome that revealed a mutation rate that is two orders of magnitude higher than previous indirect estimates, a highly biased mutational spectrum, multiple mutations affecting coding function, as well as mutational hotspots at homopolymeric nucleotide stretches.

Amino Acid Substitution↗

Microsatellites evolve more rapidly in humans than in chimpanzees.

Microsatellites are highly polymorphic markers consisting of varying numbers of tandem repeats. At different loci, these repeats can consist of one to five nucleotides. Microsatellites have been used in many fields of genetics, including genetic mapping, linkage disequilibrium analyses, forensic studies, and population genetics. It is important that we understand their mutational processes better so that they can be exploited optimally for studies of human diversity and evolutionary genetics. We have analyzed 24 microsatellite loci in chimpanzees, East Anglians, and Sub-Saharan Africans. The stepwise-weighted genetic distances between the humans and the chimpanzees and between the two human populations were calculated according to the method described by Deka et al. (1994, Genomics 22, 226-230). The ratio of the genetic distances between the chimpanzees and the humans relative to that between the Africans and the East Anglians was more than 10 times smaller than expected. This suggests that microsatellites have evolved more rapidly in humans than in chimpanzees.

Animals↗

Genetics and conservation biology.

Conservation genetics encompasses genetic management of small populations, resolution of taxonomic uncertainties and management units, and the use of molecular genetic analyses in forensics and to understanding species' biology. The role of genetic factors in extinctions of wild populations has been controversial, but evidence now shows that they make important contributions to extinction risk. Inbreeding has been shown to cause extinctions of wild populations, computer projections indicate that inbreeding depression has important effects on extinction risk, and most threatened species show signs of genetic deterioration. Inappropriate management is likely to result if genetic factors are ignored in threatened species management.

Animals↗

Detection of amplified VNTR alleles by direct chemiluminescence: application to the genetic identification of biological samples in forensic cases.

Minisatellite or variable number of tandem repeat (VNTR) regions contain such a high degree of polymorphism that they allow one to construct an individual-specific DNA "fingerprint". Analysis of these sequences by Southern blot however, consumes much DNA and is not applicable to degraded DNA samples often recovered from body-fluid stains found at crime scenes. The polymerase chain reaction (PCR) technique may overcome these problems. With oligonucleotide primers flanking the repeat region, amplification of the VNTR alleles followed by direct visualization on ethidium bromide-stained agarose gels is possible. In those cases were the PCR yield is too low for direct visualization, the product can be blotted to a nylon membrane and hybridized with a labelled internal probe. Alternatively, the PCR product can be biotinylated during amplification and visualized by direct chemiluminescence after Southern transfer. The remarkable sensitivity of the PCR technique has allowed the detection of genetic polymorphisms in single cells, hair roots and single sperm. A drawback of this very high sensitivity however is that special precautions have to be taken to prevent accidental contamination resulting in erroneous interpretation of the results.

Blood↗

Behavior of loci D1S1656 and D12S391 in a sample from Maracaibo, Venezuela.

Two recently reported short tandem repeat polymorphisms characterized by PCR, D1S1656 and D12S391, were investigated in a sample from Maracaibo, an admixed population of Venezuela, in order to evaluate their application in forensic and population genetics studies. The unbiased heterozygosities were 0.9011 and 0.8444 for locus D1S1656 and D12S391, respectively. The joint discrimination power and joint probability of exclusion were 0.99972 and 0.93287. When allele frequencies of locus D1S1656 from Maracaibo were compared with eight other populations, our group clustered with the European or European-derived samples, mainly from Spain. In the comparison of locus D12S391 with 16 populations, Maracaibo clustered with 3 Asian samples. The high heterozygosity and discrimination power make these two loci important candidates to be considered for STR packages for forensic and population genetic purposes.

Alleles↗

Estimation of allele frequencies for VNTR loci.

VNTR loci provide valuable information for a number of fields of study involving human genetics, ranging from forensics (DNA fingerprinting and paternity testing) to linkage analysis and population genetics. Alleles of a VNTR locus are simply fragments obtained from a particular portion of the DNA molecule and are defined in terms of their length. The essential element of a VNTR fragment is the repeat, which is a short sequence of basepairs. The core of the fragment is composed of a variable number of identical repeats that are linked in tandem. A sample of fragments from a population of individuals exhibits substantial variation in length because of variation in the number of repeats. Each distinct fragment length defines an allele, but any given fragment is measured with error. Therefore the observed distribution of fragment lengths is not discrete but is continuous, and determination of distinct allele classes is not straightforward. A mixture model is the natural statistical method for estimating the allele frequencies of VNTR loci. In this article we develop nonparametric methods for obtaining the distribution of allele sizes and estimates of their frequencies. Methods for obtaining maximum-likelihood estimates are developed. In addition, we suggest an empirical Bayes method to improve the maximum-likelihood estimates of the gene frequencies; the empirical Bayes procedure effects a local smoothing. The latter method works particularly well when measurement error is large relative to the repeat size, because the estimated distribution of allele frequencies when maximum likelihood is used is unreliable because of an alternating pattern of over- and underestimation. We define alleles and estimate the allele frequencies for two VNTR loci from the human genome (D17S79 and D2S44), from data obtained from Lifecodes, Inc.

Alleles↗

[Genetic polymorphisms of 6 Y-chromosome specific STR loci in the southern Chinese Han population and its application in forensic science].

To study the genetic polymorphisms of six Y-chromosome specific STR loci in the southern Chinese Han population and apply it in forensic science, six Y-STR loci were amplified by multiple PCR and the PCR products were detected by using ABI Prism 377 Sequencer. The haplotype frequencies at 6 Y-STR loci were determined in a total of 204 unrelated males from southern Han population of China. Ninety-three father/son pairs with demonstrated paternity and thirty-eight non-paternity father/son pairs were detected by using our Y-STR system. As a result, the number of alleles for DYS393, DYS19, DYS389 II, DYS390, DYS391 and DYS385 were 5, 6, 8, 6, 4 and 44, respectively. A total of 176 haplotypes at 6 Y-STR loci were found. Two father/son pairs with single Y-STR mutation were observed in the 93 father/son pairs with demonstrated paternity. Among the 38 non-paternity father/son pairs, one case with one Y-STR exclusion of paternity, one case with two Y-STR exclusions and 35 cases with 3 or more Y-STR exclusions were observed. Non-exclusion of paternity at 6 Y-STR loci was found only in one case. This result indicated that the six Y-STR loci were highly polymorphic and are suitable for personal identification and paternity testing.

Asian People↗

Molecular genetic basis of red cell markers and its forensic application.

(1) The polymerase chain reaction (PCR) was used to amplify Rh-related cDNAs from erythroid cells cultured by the selective two-phase liquid culture system for human erythroid progenitors in peripheral blood. Two Rh polypeptide cDNAs have been isolated from the PCR products and tentatively designated RhPI cDNA and RhPII cDNA. Both cDNA clones have an open reading frame composed of 1251 nucleotides. The RhPI cDNA clone shows a single nucleotide substitution with no amino acid substitution compared with the published sequence. The RhPII cDNA clone differs from the above by 41 nucleotide substitutions in the open reading frame, resulting in 31 amino acid substitutions. Besides these cDNA clones, eleven and five truncated isoforms of the RhPI and RhPII cDNAs, have been isolated, respectively. (2) The promoter region of the Duffy gene was cloned by IPCR of 1.1 kb SacI fragment and the 3' flanking sequence was cloned by IPCR of 1.9 kb EcoRI fragment. The IPCR products contained the known Duffy cDNA sequence without introns. By comparing the coding area of the Duffy gene in 28 Duffy positive individuals, we elucidated that one base change that results in an amino acid substitution (GAT(Asp44)-->GGT(Gly)) is in accordance with the Fya/Fyb polymorphism. This fact proves that the Duffy cDNA and its gene encode the Duffy blood group system. (3) Two common alleles in Esterase D (EsD) polymorphism, EsD1 and EsD2 were characterized by the substitution of one amino acid (Gly-Glu) caused by the point mutation of one nucleotide (G-A). The point mutation between cDNAs of EsD1 and EsD2 alleles was detectable as restriction fragment length polymorphism (RFLP) using Ssp1. The RFLP makes it possible to determine the EsD phenotypes using DNA samples from forensic materials without EsD enzymatic activity. (4) The authors report studies on 19 pairs of donors and recipients in bone marrow transplantation. A broad range of genetic markers at 42 gene loci, including one DNA marker 11 red blood cell markers, five human lymphocyte antigen types, 12 serum protein markers, five red cell enzyme markers, and eight salivary markers was evaluated before and after BMT over about 2 months. As a result, 11 out of 42 gene loci of genetic markers in recipients were transformed into the donor type.

Base Sequence↗

Sample size considerations in genetic polymorphism studies.

OBJECTIVES: Molecular studies for genetic polymorphisms are being carried out for a number of different applications, such as genetic disorders in different populations, pharmacogenomics, genetic identification of ethnic groups for forensic and legal applications, genetic identification of breed/stock in animals and plants for commercial applications and conservation of germ plasm. In this paper, for a random sampling scheme, we address two questions: (A) What should be the minimum size of the sample so that, with a prespecified probability, all alleles at a given locus (or haplotypes at a given set of loci) are detected? (B) What should be the sample size so that the allele frequency distribution at a given locus (or haplotype frequency distribution at a given set of loci) is estimated reliably within permissible error limits? METHODS: We have used combinatorial probabilistic arguments and Monte Carlo simulations to answer these questions. RESULTS: We found that the minimum sample size required in case A depends mainly on the prespecified probability of detecting all alleles, while in case B, it varies greatly depending on the permissible error in estimation (which will vary with the application). We have obtained the minimum sample sizes for different degrees of polymorphism at a locus under high stringency, as well as a relaxed level of permissible error. We present a detailed sampling procedure for estimating allele frequencies at a given locus, which will be of use in practical applications. CONCLUSION: Since the sample size required for reliable estimation of allele frequency distribution increases with the number of alleles at the locus, there is a strong case for using biallelic markers (like single nucleotide polymorphisms) when the available sample size is about 800 or less.

Gene Frequency↗