The mylohyoid bridge of pre-Columbian Peruvians

The frequency of expression of the mylohyoid bridge was studied in the skeletal remains of 122 Pre-Columbian Peruvians. The incidence in this population was found to be 17.6% as compared to an incidence of 15.4% found in a similar size sample population of American Negroes and a 16.1% incidence in a population of American Whites from the Terry Collection. No significant differences as to the incidence of the mylohyoid bridge were found as to the side of occurrence or between deformed and undeformed crania. A mylohyoid bridge was found in a younger individual (6 years) than had previously been reported. Females showed a significantly higher incidence of this trait in all three populations studied. A similar incidence of the mylohyoid bridge in Pre-Columbian and Mongoloid peoples adds support to the theory of a Mongoloid origin of these people. The mylohyoid bridge is considered to be a significant genetic marker which along with other such markers could be of value in population studies.     

Jugular foramen and mylohyoid bridging in an Asian Indian population

The incidence of jugular foramen and mylohyoid groove bridging was studied in a population of East Asian Indian skulls (125 males and 109 females). The criteria of Dodo (J. Anat. 144:153-165, 1986) was used in the identification of a jugular bridge. There was an overall incidence of 8.1% in jugular foramen bridging, with males showing a higher rate, though the difference did not reach statistical significance. The right side showed a statistically significant greater occurrence than the left, and the trait tended to be associated between sides. The overall incidence of mylohyoid bridging was found to be 2.6%, with no difference observed between the sexes. This frequency is less than the values reported for other Asian Indian studies. Studies concerned with the incidences of nonmetric traits such as bony bridging may be useful in population studies especially when utilized in combination, thereby enhancing the value of each trait as an anthropological tool.     

Mylohyoid and jugular foramen bridging in pre-Columbian Chileans

The occurrence of mylohyoid groove bridging and jugular foramen bridging was determined in a population of adult Pre-Columbian Chileans. Two hundred forty-one crania (110 males, 131 females) were examined for jugular foramen bridging and 464 mandibles (252 males and 212 females) were observed for mylohyoid groove bridging. The overall incidence of jugular foramen bridging was 14.94%, with females showing a higher occurrence (18.32%) than males (10.91%); however, no statistical significance was found between the sexes. The right side showed a greater incidence than the left, but again no statistical difference was noted and the occurrence of this trait was found to be associated between the sides. This frequency of jugular foramen bridging is higher than that found in other studies and approaches that reported in North American Eskimo populations. In the case of mylohyoid groove bridging, the incidence was 4.09% with no difference found between the sexes. This frequency of occurrence is less than the values reported previously for the other American populations of Mongoloid ancestry including the Pre-Columbian Peruvian population. The importance of nonmetric skeletal traits for defining population groups and their usefulness as anthropological tools is discussed. It is concluded that hard tissue variations such as bony bridging may be reliable markers to aid in discretely identifying population groups, but their importance can be significantly enhanced by coupling as many traits as possible in future studies.     

Genome-wide analysis in brazilian xavante indians reveals low degree of admixture

Characterization of population genetic variation and structure can be used as tools for research in human genetics and population isolates are of great interest. The aim of the present study was to characterize the genetic structure of Xavante Indians and compare it with other populations. The Xavante, an indigenous population living in Brazilian Central Plateau, is one of the largest native groups in Brazil. A subset of 53 unrelated subjects was selected from the initial sample of 300 Xavante Indians. Using 86,197 markers, Xavante were compared with all populations of HapMap Phase III and HGDP-CEPH projects and with a Southeast Brazilian population sample to establish its population structure. Principal Components Analysis showed that the Xavante Indians are concentrated in the Amerindian axis near other populations of known Amerindian ancestry such as Karitiana, Pima, Surui and Maya and a low degree of genetic admixture was observed. This is consistent with the historical records of bottlenecks experience and cultural isolation. By calculating pair-wise F(st) statistics we characterized the genetic differentiation between Xavante Indians and representative populations of the HapMap and from HGDP-CEPH project. We found that the genetic differentiation between Xavante Indians and populations of Ameridian, Asian, European, and African ancestry increased progressively. Our results indicate that the Xavante is a population that remained genetically isolated over the past decades and can offer advantages for genome-wide mapping studies of inherited disorders.     

An argument for the use of total side frequencies of bilateral nonmetric skeletal traits in population distance analysis: The regression of symmetry on incidence

In population studies based on frequencies of bilateral nonmetric skeletal traits, the choice between sampling by individuals or by sides should depend less on the exigencies imposed by fragmentary remains than on fundamental assumptions about the biological meaning of symmetry/asymmetry. Though the latter has been interpreted in various ways, little attention has focused on the possibility that bilateral correlation is meaningful in quantifying genetic liability for a trait. Analysis of two independent mandibular features, mylohyoid bridge and suppressed third molar, in Indian and Eskimo population samples (total N ? 1,200) reveals a statistically significant pattern of increasing bilateral occurrence with increasing population incidence. This pattern is consistent with the theory that liability for a “quasi-continuous” variant is normally distributed with constant increment between thresholds on an underlying scale. According to theory, phenotypes with more pronounced expression (bilateral occurrence) have greater genetic potential than those with less pronounced expression (unilateral occurrence). Therefore, scoring traits in total left and right sides, by giving greater weight to bilaterally affected individuals, may provide a better estimate of the liability for the trait in the population. Viewed in a theoretical context broader than that of the sampling debate, this pattern of positive regression of symmetry on incidence means that prevalence of unilateral occurrence probably cannot be used to assess the relative strength of genetic versus nongenetic control of threshold variants.     

Pre-Caucasoid and Caucasoid genetic features of the Indian population,revealed by mtDNA polymorphisms.

About 70 individuals from Punjab were examined for some mtDNA polymorphisms, namely, the RFLPs of the six classical enzymes (HpaI, BamHI, HaeII, MspI, AvaII, and Hin-cII) and for the sites AluI(7,025), DdeI(10,394), and AluI(10,397). The AluI(7,025) polymorphic site was also investigated in 96 Indians from Uttar Pradesh and Andhra Pradesh and in 163 Mediterranean Caucasoids. Moreover, 30 Indian DdeI(10,394)Alu(10,397) (++) mtDNAs were typed by the "high-resolution restriction analysis" with 14 endonucleases to estimate their divergence time. The results obtained are the following: (1) The RFLPs analysis has displayed some Caucasoid types as in Indians of Uttar Pradesh; (2) the AluI(7,025) (-) allele, which defines the most frequent Caucasoid-specific lineage (haplogroup H), ranges from 18% to 45% in the Mediterranean Caucasoids, whereas it has shown low frequencies in Punjab (6.0%) and in Uttar Pradesh (1.8%) and was not found in Andhra Pradesh; (3) the DdeI(lO,394)AluI(10,397) (+ +) haplotype, which although previously was considered an East Asian marker (haplogroup M) and was found very frequently in India, is also frequent in Punjab (27%); this frequency is, however, much lower than in Uttar Pradesh (49%) and in Andhra Pradesh (74%), and a gradient decreasing from south to north is therefore observed; (4) the divergence time of the Indian DdeI(10,394)AluI(10,397) (++) mtDNAs has been estimated to be 30,250-60,500 years, a value that is compatible with that of the homologous East Asian lineage. These results strongly support the hypothesis that the DdeI(10,394)AluI(10,397) (++) haplotype predated the Indo-European invasion and probably the split between proto-Indians and proto-Orientals. Its frequency cline well reflects the major influence of Indo-Europeans in the north and in the center of India.     

Nonmetric cranial variation and biological distances between samples of six nontribal populations of India

Sixty-nine nonmetrical morphological variants of the cranium have been studied in six samples of non-tribal, state populations in India, and their incidence reported. Using C.A.B. Smith’s angular transformation of frequencies, the multivariate Thetasquare distances and their respective standard deviations have been presented. On the basis of nonmetrical cranial variation, it is clear that the samples from Uttar Pradesh, Andhra Pradesh and Bihar are closer to each other but distant from Madhya Pradesh, Karnataka and Maharashtra. On the other hand, Karnataka and Maharashtra samples are quite close to each other and both, in turn, are comparatively closer to Madhya Pradesh than to Uttar Pradesh, Andhra Pradesh and Bihar. Madhya Pradesh sample emerges as the most divergent group among the six population samples studied. This, in general, is in conformity with the picture that emerges from various analysis of morphometric and other biological data on various populations of India.     

Distribution, endogamy, and isolation of Malas of Chittoor district, Andhra Pradesh, India

This study investigates the distribution of Malas, a scheduled caste population of Andhra Pradesh, their isolates in different eco-cultural zones, and their endogamy and isolation by marriage district. The Malas, formerly "untouchables," occupy the lowest status in the Hindu hierarchy. The sample consists of 10% of Malas from 10% of the villages in 2 taluks of Chitoor district of Andhra Pradesh. 6 Mala populations--Tangala, Maladasari, Pakanati, Rampala, Murikinati, and Bommanati--live in the area. These populations show a regionality in their distribution, with very little overlapping even when 2 populations inhabit the same village. Of 885 marriages in the 6 endogamous populations, all but 3 have been contracted between individuals belonging to the same Mala group. The 3 exogamous marriages took place between Mala men and women from another caste. Such small exceptions to the general rule do not mean that the Mala populations are not breeding isolates; these 6 populations satisfy Wright's island model. The high incidence of matings between closely related populations also contributes to their genetic and breeding isolation. Consanguineous marriages range from 26.76 to 38.75%. The distance between the birth place of spouses in miles, called marriage distance, shows a range from 7.72 to 15.71 miles. Lower values mean higher population densities. Groups within each population are isolated by distance and form small overlapping Mendelian populations, approaching a stepping stone model with continuous variation of genetic traits between adjacent groups of people.     

The St. Lawrence Island Eskimos: genetic variation and genetic distance

The Eskimos of St. Lawrence Island have been typed for genetic variation at 44 discrete genetic loci. Three private polymorphisms, at the 2,3-diphosphoglycerate mutase, peptidase B, and purine nucleoside phosphorylase loci, have been observed, which may be useful in future studies of genetic relationships between Eskimos and other circumpolar populations. Genetic distance analysis reveals a close relationship between the St. Lawrence Island Eskimos and other Eskimo populations and that the Eskimo populations form a distinct cluster from Amerindian populations. The St. Lawrence Island Eskimos appear to be more similar to Asiatic Eskimos than to other groups. Caucasian admixture in this population is estimated to be between 2 and 7%.     

Phylogeography of Aglais urticae (Lepidoptera) based on DNA sequences of the mitochondrial COI gene and control region

Mitochondrial DNA (mtDNA) sequences of the COI gene and the control region were used to examine the genetic population structure of Aglais urticae L. (Lepidoptera) over its entire geographic range, i.e., the Palaearctic. The phylogenetic relationships within and between A. urticae subspecies were determined and patterns of mtDNA divergence and ecological differentiation were compared. High gene flow together with a recent and sudden population expansion characterise the genetic population structure of this species. No geographically induced differentiation was observed, nor were subspecies identified as separate evolutionary units. The discrepancy between the genetic and ecological variation is most likely due to the slower rate of mtDNA evolution compared to ecological differentiation. The control region proved to be a less useful molecular marker for the population genetics and the phylogenetic reconstruction of closely related taxa in A. urticae than it has for other species. The extreme bias in adenine and thymine content (A+T=90.91%) probably renders this region highly susceptible to homoplasy, resulting in a less informative molecular marker.     

Polydactyly in the American Indian.

Polydactyly has an incidence in the American Indian twice that of Caucasians. A minimum estimate of this incidence is 2.40 per 1,000 live births. Preaxial type 1 has an incidence three to four times that reported for Caucasians or Negroes. The overall sex ratio in Indians is distorted with more males affected than females. The preaxial type 1 anomaly has a strong predilection for the hands and always is unilateral in contrast to postaxial type B where more than one-half are bilateral. The evidence to date, consisting of varying incidences of specific types of polydactyly among American whites, Negroes, and Indians in varying enviroments, suggests different gene-frequencies for polydactyly in each population. The incidence in Indians with 50% Caucasian admixture suggests that the factors controlling polydactyly are in large part genetically determined. Family studies and twin studies reported elsewhere offer no clear-cut genetic model which explains the highly variable gene frequencies.     

A Quantitative Comparison of the Similarity between Genes and Geography in Worldwide Human Populations

Multivariate statistical techniques such as principal components analysis (PCA) and multidimensional scaling (MDS) have been widely used to summarize the structure of human genetic variation, often in easily visualized two-dimensional maps. Many recent studies have reported similarity between geographic maps of population locations and MDS or PCA maps of genetic variation inferred from single-nucleotide polymorphisms (SNPs). However, this similarity has been evident primarily in a qualitative sense; and, because different multivariate techniques and marker sets have been used in different studies, it has not been possible to formally compare genetic variation datasets in terms of their levels of similarity with geography. In this study, using genome-wide SNP data from 128 populations worldwide, we perform a systematic analysis to quantitatively evaluate the similarity of genes and geography in different geographic regions. For each of a series of regions, we apply a Procrustes analysis approach to find an optimal transformation that maximizes the similarity between PCA maps of genetic variation and geographic maps of population locations. We consider examples in Europe, Sub-Saharan Africa, Asia, East Asia, and Central/South Asia, as well as in a worldwide sample, finding that significant similarity between genes and geography exists in general at different geographic levels. The similarity is highest in our examples for Asia and, once highly distinctive populations have been removed, Sub-Saharan Africa. Our results provide a quantitative assessment of the geographic structure of human genetic variation worldwide, supporting the view that geography plays a strong role in giving rise to human population structure.     

Estimating heritabilities and genetic correlations with marker-based methods: an experimental test in Mimulus guttatus

The calculation of heritabilities and genetic correlations, which are necessary for predicting evolutionary responses, requires knowledge about the relatedness between individuals. This information is often not directly available, especially not for natural populations, but can be inferred by using molecular markers such as allozymes. Several methods based on inferred relatedness from marker data have been developed to estimate heritabilities and genetic correlations in natural populations. Most methods use maximum-likelihood procedures to assign pairs or groups of individuals to predefined discrete relatedness classes (e.g., half sibs and unrelated individuals). The Ritland method, on the other hand, uses method of moments estimators to estimate pairwise relatedness among individuals as continuous values. We tested both the Ritland method and a maximum-likelihood method by applying them to a greenhouse population consisting of seed families of the herb Mimulus guttatus and comparing the results to the ones from a frequently used standard method based on half-sib families. Estimates of genetic correlations were far from accurate, especially when we used the Ritland method. However, this study shows that even with a few variable allozyme loci, it is possible to get qualitatively good indications about the presence of heritable genetic variation from marker-based methods, even though both methods underestimated it.     

Incidence of active tuberculosis in the native population of Canada.

We analysed the incidence rates of active tuberculosis reported between 1970 and 1981 in three groups of people born in Canada: Inuit, registered Indians and others (mainly of European origin). While the rates of tuberculosis were quite low in the last group, which constitutes about 82% of the population of Canada, they were 16 times higher among Indians and 24 times higher among Inuit. Some 20 to 30 years ago the Inuit had the highest recorded rate of tuberculosis in the world; with an intensive program the rate decreased sharply. Such a program has not been implemented among the Indian population, and the incidence rate has not decreased as rapidly. A major effort is required to satisfactorily control tuberculosis among Indians. In addition, we must not allow our efforts to slacken in the control of tuberculosis among the Inuit.     

山东胃癌高低发人群Lewis基因多态性分析

应用PCR产物直接测序的方法,检测山东省胃癌高发的临朐人群和低发的苍山人群中Lewis基因多态性T59G的分布,旨在探讨山东临朐和苍山地区胃癌发病率显著不同的内在原因,为阐明临朐地区胃癌高发的机制提供实验依据。结果表明,T59G突变个体在临朐和苍山人群中的分布频率分别为34.5%和31.6%,差别无统计学意义,P＞0.05,OR为1.14 （95% CI,0.59~2.19）。提示就此点突变而言,临朐人群和苍山人群为同一人群,具有极其相似的遗传背景;T59G不能作为区分临朐和苍山人群的遗传标志,与这两个地区胃癌发病的区别没有相关性。 Abstract:To explore the cause leading to the difference in incidence of gastric cancer between Linqu and Cangshan populations,Shandong Province,and to provide evidence for the possible mechanism of high incidence of gastric cancer in Linqu County,the distribution of T59G mutation in Lewis gene was screened between Linqu and Cangshan populations by PCR-sequencing.The frequency of individuals with T59G mutation was 34.5% in Linqu population and 31.6% in Cangshan population,respectively,with no significant difference,P＞0.05,and OR is 1.14 (95% CI,0.59~2.19).This suggests that Linqu and Cangshan populations may share the same genetic background.T59G mutation of Lewis gene could not be used as a genetic marker for Linqu and Cangshan populations and is not relevant to the difference in incidence of gastric cancer between them.     

Genetic assessment of serological and biochemical markers in Bharia tribe of Chhindwara district of Madhya Pradesh

BACKGROUND:

The present sero-genetic study is the first of its kind to present the baseline data of Bharia tribe of Madhya Pradesh. The main aim of this study is to provide phenotype and allele-frequency data to characterize the population genetically and to fill the void on the genetic map of Madhya Pradesh.

MATERIALS AND METHODS:

For this, blood samples from 92 unrelated healthy individuals of Bharia tribe from Chhindwara district (Tamia block) were collected. Hemolysates prepared were analyzed for two serological (A1A2BO and Rh) and six biochemical (adenosine deaminase, adenylate kinase locus 1, acid phosphatase locus 1, phosphoglucomutase locus 1, esterase D and glucosephosphate isomerase) parameters, following the standard electrophoretic techniques.

RESULTS:

The Chi-square test for goodness of fit revealed no significant deviation between the observed and expected numbers in any of the seven genetic markers, suggesting that the tribe is in genetic equilibrium. A high incidence of B allele in A1A2BO blood group and low incidence of the A1 allele, with presence of A2 in only one individual, and a low frequency of Rh(D) (Rh negative allele) was observed in serological markers. Also, no rare variant was observed for biochemical markers.

CONCLUSION:

Principal Component Analysis done in order to detect the genetic affinity of Bharia tribe with other populations from the adjoining states of Madhya Pradesh based on the allele frequencies, showed a close association of Bharia with Gujarat and Rajasthan. Hence, this study has been helpful in revealing the genetic structure and affinity of Bharia tribe.     

The mutation G298A-->Ala100Thr on the coding sequence of the Duffy antigen/chemokine receptor gene in non-caucasian Brazilians

Ala100Thr has been suggested to be a Caucasian genetic marker on the FY*B allele. As the Brazilian population has arisen from miscegenation among Portuguese, Africans, and Indians, this mutation could possibly be found in Euro- and Afro-Brazilians, or in Brazilian Indians. Fifty-three related individuals and a random sample of 100 subjects from the Brazilian population were investigated using the polymerase chain reaction and four restriction fragment length polymorphisms. Confirming the working hypothesis, among the related individuals three Afro-Brazilians (two of them a mother and daughter) and a woman of Amerindian descent had the Ala100Thr mutation on the FY*B allele. Five non-related Euro-Brazilians also carried the mutation. All nine individuals presented the Fy(a-b+) phenotype. We conclude that the Ala100Thr mutation can occur in populations other than Caucasians and that this mutation does not affect Duffy expression on red blood cells. Gene frequencies for this allele in the non-related individuals were in agreement with those of other populations. The Duffy frequencies of two Amerindian tribes were also investigated.     

Genetic variation across species' geographical ranges: the central-marginal hypothesis and beyond

There is growing interest in quantifying genetic population structure across the geographical ranges of species to understand why species might exhibit stable range limits and to assess the conservation value of peripheral populations. However, many assertions regarding peripheral populations rest on the long-standing but poorly tested supposition that peripheral populations exhibit low genetic diversity and greater genetic differentiation as a consequence of smaller effective population size and greater geographical isolation relative to geographically central populations. We reviewed 134 studies representing 115 species that tested for declines in within-population genetic diversity and/or increases in among-population differentiation towards range margins using nuclear molecular genetic markers. On average, 64.2% of studies detected the expected decline in diversity, 70.2% of those that tested for it showed increased differentiation and there was a positive association between these trends. In most cases, however, the difference in genetic diversity between central and peripheral population was not large. Although these results were consistent across plants and animals, strong taxonomic and biogeographical biases in the available studies call for a cautious generalization of these results. Despite the large number of studies testing these simple predictions, very few attempted to test possible mechanisms causing reduced peripheral diversity or increased differentiation. Almost no study incorporated a phylogeographical framework to evaluate historical influences on contemporary genetic patterns. Finally, there has been little effort to test whether these geographical trends in putatively neutral variation at marker loci are reflected by quantitative genetic trait variation, which is likely to influence the adaptive potential of populations across the geographical range.     

Analysis of Indian population based on Y-STRs reveals existence of male gene flow across different language groups

A study of three different Y-specific microsatellites (Y-STRs) in the populations from Uttar Pradesh (UP), Bihar (BI), Punjab (PUNJ), and Bengal (WB), speaking modern indic dialects with its roots in Indo-Aryan language, and from South of India (SI), speaking the South Indian languages with their root in Dravidian language, has shown that the predominant alleles observed represent the whole range of allelic variation reported in different population groups globally. These results indicate that the Indian population is most diverse. The similarity between the allelic variants between the populations studied by others in Africa and Asia and in this study between WB, PUNJ, UP, BI, and SI are of interest. It demonstrates that these population groups, housed in eight states of the country in different geographic locations, broadly correspond with Indo-Aryan and Dravidian language families. Further, our analyses based on haplotype frequency of different marker loci and gene diversity reveals that none of the population groups have remained isolated from others. High levels of haplotype diversity exist in all the clusters of population. Nonsignificant results based on Markov chain steps and Slatkin's linearized genetic distances indicate that there has been migration to and from in these population groups. However, some of the marginally significant interpopulation differences could be attributed to one or more of the castes with high diversity embedded within the population groups studied. Haplotype sharing between populations, F(ST) statistics, and phylogenetic analysis identifies genetic relatedness to be more between individuals belonging to two different states of India, WB and PUNJ, followed by UP and BI, whereas SI branched out separately.     

The effect of single-nucleotide polymorphism marker selection on patterns of haplotype blocks and haplotype frequency estimates

The definition of haplotype blocks of single-nucleotide polymorphisms (SNPs) has been proposed so that the haplotypes can be used as markers in association studies and to efficiently describe human genetic variation. The International Haplotype Map (HapMap) project to construct a comprehensive catalog of haplotypic variation in humans is underway. However, a number of factors have already been shown to influence the definition of blocks, including the population studied and the sample SNP density. Here, we examine the effect that marker selection has on the definition of blocks and the pattern of haplotypes by using comparable but complementary SNP sets and a number of block definition methods in various genomic regions and populations that were provided by the Encyclopedia of DNA Elements (ENCODE) project. We find that the chosen SNP set has a profound effect on the block-covered sequence and block borders, even at high marker densities. Our results question the very concept of discrete haplotype blocks and the possibility of generalizing block findings from the HapMap project. We comparatively apply the block-free tagging-SNP approach and discuss both the haplotype approach and the tagging-SNP approach as means to efficiently catalog genetic variation.