Short alleles revealed by PCR demonstrate no heterozygote deficiency at minisatellite loci D1S7, D7S21, and D12S11.

Short VNTR alleles that go undetected after conventional Southern blot hybridization may constitute an alternative explanation for the heterozygosity deficiency observed at some minisatellite loci. To examine this hypothesis, we have employed a screening procedure based on PCR amplification of those individuals classified as homozygotes in our databases for the loci D1S7, D7S21, and D12S11. The results obtained indicate that the frequency of these short alleles is related to the heterozygosity deficiency observed. For the most polymorphic locus, D1S7, approximately 60% of those individuals previously classified as homozygotes were in fact heterozygotes for a short allele. After the inclusion of these new alleles, the agreement between observed and expected heterozygosity, along with other statistical tests employed, provide additional evidence for lack of population substructuring. Comparisons of allele frequency distributions reveal greater differences between racial groups than between closely related populations.     

A population genetic study of six VNTR loci in three ethnically defined populations.

To investigate the population genetic characteristics of VNTR polymorphisms in human populations, we have studied the allele frequency distribution of six VNTR loci (D1S57, RB1, D1S77, D1S61, alpha-globin 5'HVR, D1S76) in three well-defined populations (Kachari of Northeast India; Dogrib Indian of Canada; and New Guinea Highlander of Papua New Guinea). Even though the number of alleles sampled is limited, 48 to 92 alleles per locus per population, significant variation is noticed in the number of alleles per locus for all the populations. Using alternate summary measures, we have observed that genotype distributions at the six VNTR loci apparently conform to their respective Hardy-Weinberg predictions. Multilocus genotype profiles of the individuals in each of the three populations suggest that the VNTR alleles are independently segregating with the exception of the two linked loci D1S76 and D1S77. Lack of fit of all VNTR loci to one particular model of mutational change, either the Infinite Allele Model or the Stepwise Mutation Model, suggests more than one mechanism for production of new VNTR alleles. This study also indicates that increased heterozygosity at VNTR loci in comparison to protein and blood group loci may lead to more accurate estimates of genetic distance.     

Allele frequency of VNTR locus D1S80 observed in Hb D-Los Angeles carrires

One of our previous studies presented the allele frequencies of D1S80 VNTR locus in province Denizli including the high frequencies of allele 24 and 18. In Denizli province of Turkey, the most common abnormal variant is Hb D-Los Angeles with a frequency of 57.8?% of the total abnormal Hbs. The aim of this study is to identify the allele frequencies of D1S80 VNTR locus in Hb D-Los Angeles carriers in Denizli province of Turkey. We studied unrelated 36 Hb D-Los Angeles carriers residing in Denizli province of Turkey. The size range of the D1S80 VNTR locus PCR products was determined first by agarose gel electrophoresis and then by a capillary electrophoresis system. For all subjects, DNA sequencing was performed. Allele frequency, theta (k) value, and observed and expected heterozygosity were calculated using Arlequin Software version 3.11. The most common alleles were the 24 (32?%), 18 (18.1?%) and 29 (16.7?%) alleles, and frequencies of these alleles were 0.329, 0.186 and 0.171 respectively. Other observed alleles percentages were 33, 2?%. We did not observe alleles 6, 15, 27 and 35, but we observed alleles 20 and 33. Results were in Hardy–Weinberg linkage disequilibrium. Observed heterozygosity was 0.889, and expected heterozygosity was 0.847. Theta (k) value was 4.91 (95?% confidence interval limits). According to our results, we concluded that Hb D-Los Angeles carriers have different allele frequencies in D1S80 VNTR and also have their own D1S80 VNTR locus divergence.     

Genetic structure of the Sardinian population at the D1S80 VNTR locus and population diversity

We typed the Sardinian population at the D1S80 VNTR locus. Nineteen alleles were detected in a sample of 92 unrelated individuals, allele frequency distribution showing a modal pattern mostly in agreement with other Caucasoid populations. A high degree of heterozygosity (observed value=80.4%) was present. Goodness-of-fit tests demonstrated no departure from Hardy-Weinberg expectations. Data regarding heterozygosity, number of alleles and singletons appeared in accordance with the IAM mutation-drift equilibrium model and showed no evidence of hidden substructuring. Allele 34 exhibited in Sardinians the highest frequency never observed in Caucasians. Nonetheless, the comparison with other European populations did not disclose Sardinian genetic peculiarity. Indeed, measures of genetic divergence among Europeans demonstrated definitely smaller values at the D1S80 locus in comparison with those calculated over a high number of (pre-DNA) polymorphic loci. High mutation rate and selective neutrality typical of VNTRs could account for the observed moderate genetic divergence. Isolation and genetic drift, on the other hand, may have determined certain deviations in allele frequency distribution, as occurred to allele 34 in the Sardinian population.     

Correlation of DNA fragment sizes within loci in the presence of non-detectable alleles

At present most forensic databases of DNA profiling of individuals consist of DNA fragment sizes measured from Southern blot restriction fragment length polymorphism (RFLP) analysis. Statistical studies of these databases have revealed that, when fragment sizes are measured from RFLP analysis, some of the single-band patterns of individuals may actually be due to heterozygosity of alleles in which fragment size resulting from one allele remains undetected. In this work, we evaluate the effect of such allelic non-detectability on correlation of fragment sizes within individuals at a locus, and its impact on the inference of independence of fragment sizes within loci. We show that when non-detectable alleles are present in a population at a locus, positive correlations of fragment sizes are expected, which increase with the proportion of non-detectable alleles at the locus. Therefore, a non-zero positive correlation is not a proof of allelic dependence within individuals. Applications of this theory to the current forensic RFLP databases within the US show that there is virtually no evidence of significant allelic dependence within any of the loci. Therefore, the assumption that DNA fragment sizes within loci are independent is valid, and hence, the population genetic principles of computing DNA profile frequencies by multiplying binned frequencies of fragment sizes are most likely to be appropriate for forensic applications of DNA typing data.Editor's commentsThe presence of non-detectable alleles for VNTR loci has plagued the use of these highly-discriminating systems in human identification. The authors take explicit account of these alleles, and are able to show independence of the frequencies of detectable alleles. They raise the troubling issue of how to account for occasional significant results when multiple tests are performed. By invoking Bonferroni corrections, they regard all tests, even those performed on different loci, as addressing the same hypothesis—the absence of dependence at any VNTR locus.     

Variable number of tandem repeat (VNTR) polymorphism at locus D17S5 (YNZ22) in four ethnically defined human populations

Summary We have analyzed the hypervariable locus D17S5 in four well-defined human populations (Kachari of Northeast India; Dogrib Indian of Canada; New Guinea Highlander of Papua New Guinea; and a relatively homogeneous Caucasian population of North German extraction) using both Southern blot analysis and the polymerase chain reaction (PCR) technique to; (1) compare the efficiency and limitation of Southern blotting versus PCR-based techniques in genotyping variable number of tandem repeat loci, and (2) provide allele frequency data at this locus in these four anthropologically defined populations. Preferential PCR amplification of smaller alleles associated with D17S5 was corrected by lowering the DNA template concentration to 200ng, and by reducing the extension time to 2 min. A perfect correspondence was observed between the results from Southern blot and PCR analysis in all but one sample. A very large allele, of approximately 24 to 25 repeat units, detected by Southern blotting, could not be amplified by PCR, resulting in an incorrect genotyping rate of less than 0.5%. Considering the grave consequences of mistyping in forensic and paternity testing, it is suggested that heterozygous controls consisting of large and small alleles should be employed in each PCR experiment, and PCR-generated homozygotes should be confirmed by Southern blotting. Significant variation in the number and frequency of alleles at this locus was observed in the four examined populations. A total of 15 different alleles were detected. The average heterozygosity varied from 54% in the Dogrib to 89% in the Kachari. No heterozygote deficiency was observed at this locus in any of the examined populations.     

The relevance of paternity analysis in Romanian population using the D1S80 locus

At present, DNA fingerprinting for human identification and paternity testing is a necessary and usual procedure. D1S80 is one of the best known polymorphic loci showing a VNTR, and exhibiting a high heterozygosity. This genetic locus, with a Tsp 509 I polymorphism of its 5' flanking sequence (1, 9), have been successfully amplified from human genomic DNA isolated from blood. The Tsp 509 I polymorphism was detected by restriction after PCR amplification. We tested the relevance of paternity analysis using the D1S80 locus considering the allele frequency distribution characteristic for our country. Paternal and maternal bands were compared with the children's DNA patterns. Our data include a comparison between D1S80 alleles amplified from mother, child and the supposed father for three tested families. This study was the first of this type made in Romania. We concluded a good power of discrimination and exclusion for this locus. It can be used successfully in the case of subtypes with low frequencies, and this is frequent for our population because of the high heterozygosity of D1S80 subtypes in Romanian population. We recommend the D1S80 use for exclusion paternity tests in Romanian population, as a very useful molecular tool, but we also recommend a complete set of molecular markers for confirmation paternity test in the same population.     

Amplification of reproducible allele markers for amplified fragment length polymorphism analysis.

A procedure for amplification by PCR of reproducible allele markers for amplified fragment length polymorphism (Amp-FLP) analysis is presented. We have prepared markers for the allelic products of the VNTR loci D1S80 (MCT118) and D17S30 (YNZ22) and for the hypervariable VNTR locus close to the 3' end of the apolipoprotein B gene (apoB) by re-amplifying a mixture of PCR products from individuals with known alleles. These allele markers allow precise and discrete determination of the VNTR alleles at these loci using the Amp-FLP technique that should prove suitable in forensic analyses, paternity testing and population studies.     

Allele Frequency of VNTR Locus D1S80 Observed in Denizli Province of Turkey

The variable numbers of tandem repeats (VNTR) locus D1S80, located on chromosome 1 (1p35-36), has a repeat unit 16 bp in length, and different numbers of these repeat units have been observed for populations of different origins and ethnicity. We used a molecular identification method based on capillary electrophoresis separation to analyze D1S80 locus polymorphism among 74 subjects from Denizli province, Turkey, finding an amplified fragment length size of 379–635 bp. Allele repeat numbers were deduced from these sizes and sequence comparison. The most common alleles were repeat units 24 (34.3%) and 18 (22.4%), with frequencies of 0.414 and 0.207, respectively. Other alleles were 25 (7.86%), 28 (5.71%), 22 (4.25%), and 29 (2.86%). The allele with 23 repeat units was not observed. Results were in Hardy–Weinberg linkage disequilibrium. Observed heterozygosity was 0.614, and expected heterozygosity was 0.787. Theta(k) value was 4.86 (95% confidence interval limits). Capillary electrophoresis is a powerful approach for accurate identification of VNTR loci, especially for low base pair units like D1S80, for prenatal diagnosis, linkage analysis, forensic identification, paternity testing, anthropological research, and phylogenetic studies.     

Parentage analysis for three Romanian families by DNA-fingerprinting

In forensic medicine, DNA fingerprinting for human identification and paternity testing is becoming a necessary procedure. The genetic locus D1S80 (MCT118) with Hinf I polymorphism of its 5' flanking sequence, HUMTH01 and D21S11 have been successfully amplified from human genomic DNA isolated from blood (50 ng from each sample) by the polymerase chain reaction (PCR) using oligonucleotide primers complementary to the flanking sequences as primers for amplification. DNA bands were detected by ethidium bromide staining after electrophoresis on agarose gels or high-resolution SDS-PAGE. Analysis of these VNTR loci was thus achieved without the need for Southern blot or radioactive material. The small size of the DNA fragments produced in the PCR amplification permitted good resolution of individual alleles. The precise specification of the number of tandem repeats present in each allelic fragment was reproducible from one analysis to another. The aim of this study includes three paternity testing cases; they are the first three human DNA-fingerprints performed in Romania.     

Genetic analysis of the Utah population: a comparison of STR and VNTR loci

Genetic data are reported for nine short tandem repeat (STR) loci (D3S1358, vWA, FGA, D8S1179, D21S11, D18S51, D5S818, D13S317, and D7S820) and six variable number of tandem repeat (VNTR) loci (D2S44, D10S28, D4S139, D1S7, D5S110, and D17S79) in samples of Utah African Americans, European Americans, and Hispanics. Little evidence of departures from Hardy-Weinberg equilibrium or gametic equilibrium was found in these populations. Because of their relatively higher mutation rates, the VNTR loci exhibited higher average heterozygosity and lower FST levels than did the STR loci. Genetic distance analysis showed congruence between the two types of systems, and a genetic distance analysis of the STR data showed that the three Utah populations are genetically similar to the same ethnic groups in other parts of the United States. In addition, this analysis showed that the African American population is the most genetically divergent, with greater similarity between the Hispanic and European American populations. This analysis demonstrates a high degree of consistency for population designations commonly used in forensic analysis.     

Linkage mapping of highly informative DNA polymorphisms within the human interferon-alpha receptor gene on chromosome 21.

Two polymorphic loci within the interferon-alpha receptor (IFNAR) gene on human chromosome 21 have been identified and mapped by linkage analysis in 40 CEPH families. These markers are (1) a multiallelic RFLP with an observed heterozygosity of 0.72 and (2) a variable (AT3)n short sequence repeat at the poly(A) tail of an Alu sequence (AluVpA) with an observed heterozygosity of 0.83. This locus is close to D21S58 (theta = 0.02, zeta = 36.76) and D21S17 (theta = 0.02, Zeta = 21.76) with chromosomal band 21q22.1. Multipoint linkage analysis suggests the most likely locus order to be 21cen-D21S58-IFNAR-D21S17-21qter. Given its high heterozygosity, the IFNAR gene can be used as an index marker on human chromosome 21.     

Characterization of three VNTR systems at D21S112.

D21S112 is a highly polymorphic marker on the long arm of chromosome 21. Our analysis of this locus indicated the presence of three VNTR systems. We estimated the heterozygosity of each system and sequenced one of the repetitive regions. Utilizing PCR, we demonstrated that the sequenced VNTR is responsible for the system with the highest level of heterozygosity. Combining data from the three systems makes D21S112 one of the most informative loci on the chromosome.     

Characterization of <Emphasis Type="Italic">TPMT</Emphasis> minisatellite locus in five ethnic groups of India

A total of 206 random, healthy individuals belonging to five distinct ethnic groups (Ezhavas, Arayas, Nairs, Vishwakarmas and Muslims) were analyzed for 18 bp VNTR repeat polymorphism present in the 5í flanking region of the Thiopurine Methyl Transferase gene (TPMT). In the present study, the population data of TPMT minisatellite was compared with the population data of other loci and the utility of minisatellite was evaluated in population studies. Human tandem repeat alleles of the TPMT minisatellite locus were characterized for the length polymorphism. The expected and observed heterozygosity did not show any significant difference. All five populations were in Hardy-Weinberg equilibrium. High polymorphism information iontent (PIC) (≥0.658) and power of discrimination (PD) (ranging from 0.775–0.860) value of this VNTR showed that this marker is informative. The combined power of discrimination of TPMT minisatellite along with other two loci studied earlier in our lab was 0.9964. The paternity exclusion power (PE) of TPMT VNTR ranged from 0.203 to 0.533 and the combined power of paternity exclusion (with two other loci D8S315 and D2S1328) was ≥0.8285. All these parameters (heterozygosity, PD, PIC, PE) of TPMT minisatellite locus showed that this marker is informative and can be used for DNA typing and population studies besides being used in clinical investigation in checking thiopurine drug sensitivity of individuals. The text was submitted by the autor in English.     

Genetic polymorphism study at four minisatellite loci (D1S80, D17S5, D19S20, and APOB) among five Indian population groups

The present study reports the genetic variation observed among five anthropologically distinct population groups of India, using four highly polymorphic minisatellite loci (D1S80, D17S5, D19S20, and APOB 3' VNTR) in order to examine the effect of geographical and linguistic affiliations on the genetic affinities among these groups. Random individuals from five ethnic groups were studied; the sample size ranged from 235 to 364. The population groups belong to two geographically separated regions of India, the state of Maharashtra (western India) and the state of Kerala (southern India). The two Maharashtrian groups (Konkanastha Brahmins and Marathas) speak "Marathi," an Indo-European language, whereas the three Kerala population groups (Nairs, Ezhavas, and Muslims) speak "Malayalam," an Indo-Dravidian language. Genomic DNA was extracted from peripheral blood samples and analyzed using amplified fragment length polymorphism (Amp-FLP) technique. All four loci displayed high heterozygosity with average heterozygosity in the range of 0.82 to 0.84. The Polymorphic Information Content and Power of Discrimination were > or = 0.75 and > or = 0.80, respectively. The coefficient of gene differentiation was found to be low (average G(ST) = 1.2%; range between 0.6% at D1S80 locus to 1.6% at APOB 3' VNTR locus) across the loci, indicating close affinity among the population groups. The neighbor-joining tree revealed two clear clusters, one for the two Maharashtrian population groups and the other for the three Kerala population groups. The results obtained are in conformity with the geographical and linguistic backgrounds of the studied populations.     

VNTR loci reveal differentiation between and structure within populations of the eastern barred bandicoot Perameles gunnii

The Eastern Barred Bandicoot Perameles gunnii has declined in abundance within mainland south-eastern Australia, to a relict wild population of less than 100 individuals in Hamilton, Victoria. It is more common, but is also declining in Tasmania. Genomic DN A variability was compared within and between surviving populations of P. gunnii using variable number of tandem repeat (VNTR) markers in one of two ways. First, average percentage differences (APDs) were determined between profiles for two VNTR probe—endonuclease combinations. Secondly, because one of these combinations revealed two multiallelic VNTR loci, genotypes were assigned and analysed for homogeneity of allele frequencies among subpopulations, for deviation of heterozygosity from Hardy-Weinberg equilibrium within populations and for genetic structuring among individuals from different subpopulations. The results of both the APD and defined locus approaches showed consistent trends within and between populations. Genetic variability was higher among mainland P. gunnii than in Tasmanian populations (higher APDs, number of alleles, and heterozygosity at one locus), despite the known decline and subdivision of the Hamilton population. Eleven per cent of the variability detected in Hamilton was attributed to genetic differentiation between east and west subdivisions of the population. Departure from random mating indicating local inbreeding within collecting localities was evident for one locus in both north and south Tasmania, particularly at one locality. AH alleles at both loci were unique to either Hamilton or Tasmanian P. gunnii. The initial captive colony contains high heterozygosity for these loci. It is concluded that VNTR markers can be of benefit for use in studies of population differentiation and for conservation management.     

北京地区汉族群体D1S1612和D18S535基因座的遗传多态性

采用扩增片段长度多态性（Amp-FLP）分型技术,调查中国北京地区汉族群体D1S1612、D18S535 基因座的遗传多态性,获得等位基因频率分布。结果显示, D1S1612检出9个等位基因,25种基因型, D18S535检出9个等位基因,27种基因型。两个STR基因座的杂和度（H）分别为0.779、0.887;个人识别率（Dp）分别为0.901、0.927;非父排除率（PE）分别为0.564、0.770;多态信息容量（PIC）分别为0.723、0.796,卡方检验表明两个STR 基因座基因型频率分布符合Hardy-Weinberg平衡 (P>0.01 )。D1S1612和D18S535 基因座均属高杂合度、高识别能力的遗传标记,可用于法庭科学亲子鉴定和个人识别。 Abstract: To investigate the genetic polymorphism of D1S1612 and D18S535 in Han population of Beijing. Amp-FLP method was used. 9 alleles, 25 genotypes were observed for D1S1612 locus; and 9 alleles and 27 genotypes for D18S535 locus. All allele frequencies, heterozygosity (H), discrimination power (Dp), exclusion of paternity probability (PE) and polymorphism information content (PIC) were calculated. The allele distributions of the two loci were conformed to Hardy-Weinberg equilibrium (P>0.01). According to the results obtained in this study, it is suggested that both D1S1612 and D18S535 are useful genetic markers for individual identification and paternity testing in forensic science practice as well for genetic study.     

Frequency of the hypervariable DNA loci D18S849, D3S1744, D12S1090 and D1S80 in a mixed ancestry population of Chilean blood donors

Blood donors (N = 150) at San José Hospital (Santiago, Chile) were typed for one VNTR locus (D1S80) and three STR loci (D18S849, D3S1744, D12S1090). A questionnaire was used to determine the socioeconomic level of the donors, because it is known that some genetic markers (e.g., the ABO and Rh groups) are differentially distributed between different socioeconomic strata. This methodology revealed that two of the three socioeconomic strata distinguishable in Santiago were present in our sample of blood donors, with stratum II representing the middle strata and stratum III the low strata. Allele frequency was determined for each locus and socioeconomic stratum, and it was found that the allele distributions of each locus in socioeconomic strata II and III were statistically similar. All loci conformed to the Hardy-Weinberg law and there was no evidence for association between the alleles of the four loci, allelic frequencies being similar to those found in North American Hispanic populations. The results support the view that the analysis of these loci may have useful applications in population genetics as well as in identity tests.     

Characterization of eight VNTR loci by agarose gel electrophoresis

Allelic frequencies and their confidence intervals were obtained for eight independent VNTR loci from a sample of more than 75 Utah Caucasians. Using high-resolution agarose gel electrophoresis, we were able to resolve alleles at the D17S5 locus that differed by only one repeating unit; it was therefore possible to name the alleles according to the number of repeating units each contained. Two a priori probabilities were calculated for each VNTR locus separately and for all eight loci jointly: (i) the "power of exclusion" for an alleged father/mother/child trio and for an alleged parent/child duo, and (ii) the "probability of matching" when two unrelated individuals or two siblings are genotyped.     

Isolation and characterization of a highly polymorphic human locus (DXS455) in proximal Xq28

Human Xq28 is highly gene dense with over 27 loci. Because most of these genes have been mapped by linkage to polymorphic loci, only one of which (DXS52) is informative in most families, a search was conducted for new, highly polymorphic Xq28 markers. From a cosmid library constructed using a somatic cell hybrid containing human Xq27.3----qter as the sole human DNA, a human-insert cosmid (c346) was identified and found to reveal variation on Southern blot analyses with female DNA digested with any of several different restriction endonucleases. Two subclones of c346, p346.8 and p346.T, that respectively identify a multiallelic VNTR locus and a frequent two-allele TaqI polymorphism were isolated. Examination of 21 unrelated females showed heterozygosity of 76 and 57%, respectively. These two markers appeared to be in linkage equilibrium, and a combined analysis revealed heterozygosity in 91% of unrelated females. Families segregating the fragile X syndrome with key Xq28 crossovers position this locus (designated DXS455) between the proximal Xq28 locus DXS296 (VK21) and the more distal locus DXS374 (1A1), which is proximal to DXS52. DXS455 is therefore the most polymorphic locus identified in Xq28 and will be useful in the genetic analysis of this gene dense region, including the diagnosis of nearby genetic disease loci by linkage.