Degree Of Admixture Research Articles

Y-chromosome lineages in São Tomé e Príncipe and Cabo Verde islands: Different input of European influence

The Y-chromosome haplogroup composition of the population of São Tomé e Príncipe and Cabo Verde Archipelagos was profiled by using 24 biallelic markers, and compared with populations from Europe, Africa and the Middle East. According to the traditional view, these archipelagos colonized by the Portuguese in the 15th century were settled mainly by West African slaves, with the addition of a minor fraction of male colonizers from Europe. Although the major proportion of the founding population of São Tomé e Príncipe cluster in haplogroup E3a (84.2%), very common among sub-Saharans, this lineage was observed at a frequency of only 15.9% in Cabo Verde. Haplogroups I, J and R1, characterized of populations of Europe and the Middle East account for more than half of the paternal lineages of Cabo Verdeans (53.5%). These West Eurasian haplogroups are found at a frequency of only 12.5% in the population of São Tomé e Príncipe. Our findings suggest that despite the sub-Saharan genetic background of these archipelagos, a relevant contribution of European paternal lineages is present in nowadays populations indicating that gene flow from multiple sources have been important in the formation of the diversity of the islanders, nevertheless with a different degree of admixture.

Comparison of the rapidly evolving KIR locus in Parsis and natives of India

The extreme variability at the Killer cell Immunoglobulin-like Receptor (KIR) locus along with that of the genes encoding their ligands, HLA class I, appears to modulate risk for viral, autoimmune, and malignant diseases, and reproductive failure. Differences in KIR gene and haplotype frequencies across world populations may reflect some combination of ancestral genotypes, locale-specific selection pressures, and genetic drift. We genotyped unrelated healthy Parsis and Maharashtrian Hindus, neighboring peoples from Western India. These two populations showed remarkable similarity in KIR gene frequencies despite their distinct ethnic background and the fairly recent migration of Parsis to Western India from Persia around 900 A.D: . One clear exception is KIR3DS1, which is found at a significantly higher frequency in the Parsis than in the Maharashtrians, previously characterized North Indians, and most other world populations. The high KIR3DS1 frequency of Parsis corresponds with a low frequency of its putative HLA-B ligand group, an inverse correlation that has been observed previously across other world populations. Thus, KIR3DS1 frequency in Parsis may be a remnant of their distinct ancestral Persian origin. KIR gene frequencies and profiles of the Parsis and Maharashtrians were more similar to one another than they were to North Indians, suggesting a potential effect of local environmental factors on KIR evolution and/or some degree of admixture between Parsis and populations from Western India. Overall, these data support other studies indicating the rapid evolution of the KIR locus and the apparent dependency of this evolution on the loci encoding HLA class I ligands.

Cioclovina (Romania): affinities of an early modern European

The current modern human origins debate centers on the possibility and degree of admixture between indigenous archaic humans and modern human populations migrating out of Africa into Europe and Asia in the Late Pleistocene. Evidence for such admixture must be sought in the earliest fossil record of modern humans outside Africa, as it is those populations that would have encountered, and possibly interbred with, archaic hominins. In the case of Europe, the recent application of direct dating techniques has eliminated several specimens from the Upper Paleolithic fossil record, while confirming early ages for others. Among these earliest reliably dated specimens is the Cioclovina calvaria from Romania. This individual is of highest importance for the understanding of modern human origins in Europe, and has recently been proposed to represent a Neanderthal-modern human hybrid. We present a short description and a three-dimensional (3D) geometric morphometric analysis of the Cioclovina specimen using a large geographic sample of recent humans, Neanderthals and Middle and Late Pleistocene fossil hominins from Europe, Africa, and the Levant, in order to establish its phenetic affinities and to evaluate its morphology for evidence of admixture between Neanderthals and early modern Europeans. Our results show Cioclovina to be entirely modern in its cranial shape, and do not support the hypothesis that it represents a hybrid.

Genetic Diversity and Population Structure of Wild Olives from the North-western Mediterranean Assessed by SSR Markers

This study examines the pattern of genetic variability and genetic relationships of wild olive (Olea europaea subsp. europaea var. sylvestris) populations in the north-western Mediterranean. Recent bottleneck events are also assessed and an investigation is made of the underlying population structure of the wild olive populations. The genetic variation within and between 11 wild olive populations (171 individuals) was analysed with eight microsatellite markers. Conventional and Bayesian-based analyses were applied to infer genetic structure and define the number of gene pools in wild olive populations. Bayesian model-based clustering identified four gene pools, which was in overall concordance with the Factorial Correspondence Analysis and Fitch-Margoliash tree. Two gene pools were predominantly found in southern Spain and Italian islands, respectively, in samples gathered from undisturbed forests of the typical Mediterranean climate. The other two gene pools were mostly detected in the north-eastern regions of Spain and in continental Italy and belong to the transition region between the temperate and Mediterranean climate zones. On the basis of these results, it can be assumed that the population structure of wild olives from the north-western Mediterranean partially reflects the evolutionary history of these populations, although hybridization between true oleasters and cultivated varieties in areas of close contact between the two forms must be assumed as well. The study indicates a degree of admixture in all the populations, and suggests some caution regarding genetic differentiation at the population level, making it difficult to identify clear-cut genetic boundaries between candidate areas containing either genuinely wild or feral germplasm.

HLA genes in Cubans and the detection of Amerindian alleles

Caribbean Islands including Cuba were first inhabited by Meso-American and later by Arawak-speaking Amerindians from nowadays Venezuela. Spanish invaders brought to almost extinction to the Amerindian population after 1492. Black slaves from West Africa were taken into Cuba by Europeans. The degree of admixture among populations is approached. HLA alleles were studied by DNA techniques. Comparison with other worldwide populations (a total of 14.094 chromosomes) included genetic distances, Neighbour-Joining dendrograms, correspondence analyses and calculation of extended haplotypes. While African-European HLA features were clearly found, Amerindian HLA characteristics are less evident, indicating that Amerindian devastation was particularly marked after 1492 AD. However, typical Amerindian alleles have been found in our Cuban sample, i.e. DRB1*0403, DRB1*0404, DRB1*0407, BRB1*0411, DRB1*0802 and DRB1*0809. The presence of Amerindian alleles in Cubans may have a bear in the making up of transplantation registries (both for bone marrow and solid organ transplantation) at the regional level and also be important for epidemiological studies of diseases linked to HLA.

Using ancestry-informative markers to define populations and detect population stratification

A serious problem with case-control studies is that population subdivision, recent admixture and sampling variance can lead to spurious associations between a phenotype and a marker locus, or indeed may mask true associations. This is also a concern in therapeutics since drug response may differ by ethnicity. Population stratification can occur if cases and controls have different frequencies of ethnic groups or in admixed populations, different fractions of ancestry, and when phenotypes of interest such as disease, drug response or drug metabolism, also differ between ethnic groups. Although most genetic variation is inter-individual, there is also significant inter-ethnic variation. The International HapMap Project has provided allele frequencies for approximately three million single nucleotide polymorphisms (SNPs) in Africans, Europeans and East Asians. SNP variation is greatest in Africans. Statistical methods for the detection and correction of population stratification, principally Structured Association and Genomic Control, have recently become freely available. These methods use marker loci spread throughout the genome that are unlinked to the candidate locus to estimate the ancestry of individuals within a sample, and to test for and adjust the ethnic matching of cases and controls. To date, few case-control association studies have incorporated testing for population stratification. This paper will focus on the debate about the quantity and methods for selection of highly informative marker loci required to characterize populations that vary in substructure or the degree of admixture, and will discuss how these theoretically desirable approaches can be effectively put into practice.

Unmuddling the Debate on Human Diversity

Unmuddling the Debate on Human Diversity Race (The Reality of Human Differences) Vincent Sarich and Frank Miete Westview Press, Boulder (Co) 2004 A Silly Debate The thesis of this book is simple enough: Differences between human races are real; they are of substantial magnitude; and they are, sometimes at least, important. The naive observer will object that there is little originality in this thesis. After all, every hairdresser knows that there are important race differences. At least, every hairdresser in the Caribbean knows it. The ostensible reason for this book's existence is that some intellectuals don't seem to know it. During the past half-century, articles claiming that race differences are minimal, unimportant, or non-existent have proliferated both in the popular press and in academic journals-including even The Mankind Quarterly (Biondi and Rickards, 2002). Sarich's and Miele's logic is not too different from the hairdresser's, although their book is written for intellectuals rather than hairdressers. The authors are well placed to write about this subject. Vincent Sarich has been one of the leading figures in population genetics for the past 30 years, and his work on the molecular clock arid its application to human evolution has been a major contribution to our current understanding of modern human origins. Frank Miele is editor of Skeptic magazine, where the debunking of pseudoscience and popular superstition is part of his job description. The academic debate about the non-existence of race is a rhetorical controversy rather than a substantive one, revolving around the definition of the term race. The impetus behind the claim that race does not exist is not scientific but normative, modeled on the newspeak in Orwell's 1984: the belief that people's thoughts are determined by the categories made available by their language. If we remove the term race from our vocabulary, racism will end because people can no longer think about race differences and their implications. Never mind that the Sapir-Whorf hypothesis of linguistic determinism has not fared too well in the scientific arena (Pinker, 1994). This fruitless academic debate with its surrealistic touch and Orwellian undertones is unsuitable for any book aimed at a wider audience. But fortunately, Sarich and Miele are not interested in rhetoric but in the real thing: not what is in our heads, but what is in the world. The authors start by showing that the reality of race differences is sell-evident to the layman and is taken for granted by the legal system. Common people can tell a Japanese from a Kenyan on first sight. Only some intellectuals can't. But molecular biologists can. True, the majority of genetic diversity among humans is within rather than between races, but some genetic markers do vary substantially among races. Sarich describes how a person's race can be determined from his DNA. In the latest version of the DNAPrint method, used in forensics, information from 73 DNA polymorphisms is combined to determine not only a person's race, but even the degree of admixture with great accuracy. If you happen to be 85% African and 15% Native American, the DNA test will show it! Nor is the awareness of race differences limited to modern societies. Miele shows that the early Egyptian, Greek, Indian, Chinese and Arab civilizations all distinguished races not only by their physical appearance, but also attributed behavioral characteristics to them. Race prejudice is not a modern invention but can be traced through the ages! The authors proceed by tracing the modern history of ideas about race differences, starting with the pre-Darwinian opposition between monogenists and polygenists: those who believed that people were created by God only once and developed into separate races only recently, and those who believed that the races were created separately. And on it goes through the post-Darwinian controversies that finally led to the widespread denial of race differences in the late 20lh century: between Ernst Haeckel and Rudolf Virchow, Franz Boas and Madison Grant, and between Carleton Coon and Ashley Montagu. …

Ultrasound attenuation and collective modes in mixed d x2-y2 + id xy state of unconventional superconductors

We discuss two methods used for the study of unconventional superconductors: ultrasound attenuation and collective modes. These two methods, as well as microwave absorption, turn out to be coupled and have become very important now. Within models built by path integration technique we analyze some recent ideas concerning possible realization of the mixture of different d-wave states in high temperature superconductors (HTSC).We specifically consider the mixture of d x2-y2 and d xy states. We study the collective mode spectrum and the ultrasound attenuation in the mixed state, and show that each of the two methods allows us to distinguish a pure d-wave state from a mixed one. They also allow us to identify the type of pairing and order parameter in unconventional superconductors, including the presence and topology of gap nodes, the magnitude of the gap, and degree of admixture in the mixed state.

Population data on D7S820, FGA, D1S533 and D9S304 in a sample of Caucasian-Mestizos from Colombia

1. IntroductionShort tandem repeats (STR) are widely used in forensics as well as in paternity testing[1–4]. However, before a new marker system can be introduced into forensic casework, apopulation database for the relevant population must be established for statisticalevaluation of the evidence.The population of Colombia with nearly 41 million people is composed of three ethnicgroups [5]. The Caucasian-Mestizo population represents the majority of the population,composed mainly of inhabitants of Spanish descent and, in a minor degree, of otherEuropean, Arab and Jewish populations. However, in certain regions (Pacific coast,Caribbean coast and islands), Colombians of African origin are the predominant group[6]. The third ethnic group, the Amerindians, are located mainly in the plains, theAmazonian jungle, in some regions of the Colombian Andes (southwest) and in thenortheast section of the country [7,8]. Previous studies have revealed different degrees ofgenetic admixture in different regions of the country [9]. In the Andean region, theCaucasian-Mestizo population predominates, showing different degrees of admixture,mainly with Amerindians. In the Pacific and Caribbean, coast individuals of African originpredominate where different degrees of admixture are present.We have previously reported the population frequencies for several STR loci [10–13].This report presents allele frequency data in a sample of Caucasian-Mestizos from the

Molecular analysis of HLA class II polymorphisms among different ethnic groups in Israel

The Jewish population in Israel comprises of inhabitants of heterogeneous ethnic backgrounds. Genetic studies classify the Israeli Jewish population into two major groups: Ashkenazi from Central and Eastern Europe and Sephardic or non Ashkenazi, from the Mediterranean and North Africa. The present study was aimed at elucidating the differential influx of HLA class II alleles in Ashkenazi, in various non-Ashkenazi subgroups and in Israeli Moslem Arabs. Using the PCR-SSOP technique, a large number of alleles were detected at each of the loci examined (DRB1, DQA1 and DQB1). In addition, gene frequencies, characteristic DR/DQ linkage disequilibria, population distances and their corresponding dendogram, were used to study the relationship between Israelis as a group, non Jewish Caucasians and Blacks. These populations could be grouped into three main clusters: the first consists of all the Israeli groups with the exception of the Ethiopian Jews; the second consists of non Jewish Caucasians, with a clear distinction seen between Israelis and non Jewish Europeans and U.S. Caucasians; the third, composed of Blacks, is distinctly different from the other populations. Ethiopian Jews were found to be closer to the Blacks than to any of the Israeli Jewish groups. We have shown that Jews share common features, a fact that points to a common ancestry. A certain degree of admixture with their pre-immigration neighbors exists despite the cultural and religious constraints against intermarriage.

Analysis of mtDNA HVRII in several human populations using an immobilised SSO probe hybridisation assay.

Several populations were typed for the hypervariable region II (HVRII) of the mitochondrial DNA (mtDNA) control region using immobilised sequence-specific oligonucleotide (SSO) probes. A total of 16 SSO probes was used to type 1081 individuals from eight different ethnic groups (African Americans, Somali, US Europeans, US Hispanics, Bosnians, Finns, Saami and Japanese). Data was compared with already published sequence data by analysis of principal components, genetic distances and analysis of the molecular variance (AMOVA). The analyses performed group the samples in several clusters according to their geographical origins. Most of the variability detected is assigned to differences between individuals and only 7% is assigned to differences among groups of populations within and between geographical regions. Several features are patent in the samples studied: Somali, as a representative East African population, seem to have experienced a detectable amount of Caucasoid maternal influence; different degrees of admixture in the US samples studied are detected; Finns and Saami belong to the European genetic landscape, although Saami present an outlier position attributable to a strong maternal founder effect. The technique used is a rapid and simple method to detect human variation in the mtDNA HVRII in a large number of samples, which might be useful in forensic and population genetic studies.

Anisotropic magnetic field effects in diluted magnetic semiconductor quantum wells

A theoretical formalism has been developed for calculating the effects of an externally applied magnetic field in both the Faraday and Voigt configuration for diluted magnetic semiconductor structures. The analysis has been applied to the magnetic field dependence of exciton transition energies and of exciton magnetic-polaron energies. Marked anisotropies with respect to the Faraday and Voigt configurations are observed in both cases. The results are interpreted in terms of the different degrees of admixture of light- and heavy-hole states as a function of the field. A comparison with experimental observations enables conclusions to be drawn with regard to important questions such as the degree of interface roughness and the extent of exciton localization in these structures.

EVOLUTION AND POPULATION STRUCTURE OF AFRICANIZED HONEY BEES IN BRAZIL: EVIDENCE FROM SPATIAL ANALYSIS OF MORPHOMETRIC DATA.

In recent years, studies based on isoenzymatic patterns of geographic variation have revealed that what is usually called the Africanized honey bee does not constitute a single population. Instead, several local populations exist with various degrees of admixture with European honey bees. In this paper, we evaluated new data on morphometric patterns of Africanized honey bees collected at 42 localities in Brazil, using univariate and multivariate (canonical) trend surface and spatial autocorrelation analyses. The clinal patterns of variation found for genetically independent characters (wing size characters and some wing venation angles) are concordant with previous studies of malate dehydrogenase (MDH) allelic frequencies and support the hypothesis that larger honey bees in southern and southeastern Brazil originated by racial admixture in the initial phases of African honey bee colonization. Geographic variation patterns of Africanized honey bee populations reflect a demic diffusion process in which European genes were gradually lost because of the higher fitness of the African gene pool in Neotropical environmental conditions.

Complement C3 polymorphism in sixteen populations of Colombia. Results of “Expedicion humana”

Blood samples of 1.022 individuals of both sexes, collected during the “Expedicion Humana” programme. Twelve Indian group, two Negroes, two urban and one mestizo populations of Colombia were C3 typed. The results showed the urban samples have C3*F genotype frequencies (17 and 20%) similar to the Spanish population. The Negroe system, with lower C3*F gene frequencies (3.5 and 7%) also resembled their parental populations in Africa. The Mestizo population reported in this study showed a lower value of the C3*F gene (2.2%) than previously studied. suggesting that the degree of admixture may vary in different regions of the country. As regards the Indian populations, there was a wide range of variation of the C3*F gene (0–19%) many tribes being monomorphic. This gene may be a marker of recent admixture in Amerindians, but there may be other genetic factors, such as selection and inbreeding in maintaining high levels of genetic polymorphism in tribes such as Guahibo.

Analysis of HLA class II allogenotyping in Australian aborigines and Papua New Guinea populations.

Human leukocyte antigen (HLA) class II allogenotyping has been applied to investigate the polymorphism of the DRB, DQB1, DQB2, DQA1, and DQA2 genes in Aborigines from the East Coast of Australia and in Melanesians from the Papua New Guinea North-East Coast and Highlands. Three new DR/DQ arrangements were observed, DRw14/DQB1-2b/DQA1-1a and DRw5Nauru/DQB1-3a/DQA1-2 (n Australian Aborigines), and DRw5Nauru/DQB1-1a/DQA1-1b (in Madang). DQA2 and DQB2 allogenotyping with TaqI and PstI digested genomic DNA revealed little polymorphism among the Papua New Guineans, with DQA2-Xa1 and DQB2-Xb1 the most common alleles in all the groups. However, the presence of DQA2-Xa2 in Papuans and Australian Aborigines reflects the degree of admixture with Caucasoids while the DQA2-Xa4 allele in Madang is probably a marker of Mongoloid origin.

Genealogical and genetical African admixture estimations, blood pressure and hypertension in a Caribbean community

This study examines the relationships between blood pressure, prevalence of hypertension, and the degree of black African admixture in the population of the Caribbean Island of La Désirade which is homogeneous with respect to the environmental factors and for which the socioeconomical stratification does not match racial origin. The degree of admixture was estimated by using both genealogical information and genetic markers. Blood pressure was repeatedly measured using an automatic sphygmomanometer. After adjustment for age, sex, ponderal index, Na/K urinary ratio, and clinical alcoholism, blood pressure and prevalence of hypertension were found to be significantly higher for the individuals having the largest proportion of genes of black origin. Identical results were obtained when either genetic markers or genealogical information were used as an individual--estimator of admixture.

The density of states of Ag impurities in Cd determined by Auger and photoelectron spectroscopy

The Ag density of states of Cd97Ag3 is shown to be well described by a Clogston-Wolff model with parameters Delta =4.5 eV and pi V2p=0.35 eV. This model density of states, when combined with the Ag 4d spin-orbit splitting, correctly describes the Ag virtual bound state observed by photoemission. The Auger profile of the AgM4.5N4.5N4.5 transitions are shown to be in good agreement with calculated profiles which combine the Cini/Sawatzky theory with atomic-structure calculations and the Clogston-Wolff model of the Ag density of states. The Auger study shows that the Coulomb repulsion between two holes localised on a Ag site, U(1G4), is 4.1 eV+or-0.2 eV. The Auger profile is found to be very sensitive to the degree of admixture of the Ag states into the Cd d band and is consistent with the 3.2% admixture predicted by the Clogston-Wolff model.

Effects of oil on water filtration by exposed sandy beaches

The most important natural function of exposed sandy beaches is the filtration of large volumes of sea water which are flushed through the interstitial pore system by the actions of tides and waves. In this process organic material is mineralized by the interstitial fauna and nutrients returned to the sea. This paper examines the physical effects of oil in blocking or reducing this filtration. Reduced filtration of sea water may be caused by prevention or retardation of interstitial water flow and/or decrease in pore space. The magnitude of the effects depends on the volume of oil, its state of weathering, its location on the beach and its degree of admixture with sand. It appears that under all but the heaviest conditions of pollution these effects are relatively small and only become significant in situ when discrete layers of weathered oil occur near the surface in the upper intertidal zone where maximum water input normally occurs.

A study of some genetic characteristics of the population of the Sudan.

300 random blood samples collected from residents of Khartoum, Sudan, were analysed for 5 blood group systems, 4 serum proteins, 9 red cell enzymes, abnormal haemoglobins and beta-thalassaemia. The results suggest varying degrees of admixture of the local tribes by migration from the surrounding regions. Two samples showed a probable new variant of glucose 6-phosphate dehydrogenase (? GdB Khartoum) with normal red cell activity. In spite of the presence of a high degree of consanguinity in the population, there was no significant deviation from Hardy-Weinberg equilibrium in any of the polymorphic systems.

The Tamang: A Case of Hybridization

The Tamang, a Mongoloid and hybrid population of the eastern part of the cis-Himalayan region of West Bengal, have been studied for an estimation of the Tibetan and Nepalese components. The degree of admixture of the two parental stocks is found to be about 59 and 41%, respectively. The deviation between the observed and expected gene frequencies of the hybrid is insignificant.