RESUMO
The American continent was the last to be occupied by modern humans, and native populations bear the marks of recent expansions, bottlenecks, natural selection, and population substructure. Here we investigate how this demographic history has shaped genetic variation at the strongly selected HLA loci. In order to disentangle the relative contributions of selection and demography process, we assembled a dataset with genome-wide microsatellites and HLA-A, -B, -C, and -DRB1 typing data for a set of 424 Native American individuals. We find that demographic history explains a sizeable fraction of HLA variation, both within and among populations. A striking feature of HLA variation in the Americas is the existence of alleles which are present in the continent but either absent or very rare elsewhere in the world. We show that this feature is consistent with demographic history (i.e., the combination of changes in population size associated with bottlenecks and subsequent population expansions). However, signatures of selection at HLA loci are still visible, with significant evidence selection at deeper timescales for most loci and populations, as well as population differentiation at HLA loci exceeding that seen at neutral markers.
Assuntos
Indígena Americano ou Nativo do Alasca/genética , Demografia , Loci Gênicos , Antígenos HLA/genética , Seleção Genética , Alelos , Variação Genética , Geografia , Haplótipos/genética , Heterozigoto , Homozigoto , Humanos , Repetições de Microssatélites/genética , América do Norte , Tamanho da Amostra , América do SulRESUMO
The possibility of voyaging contact between prehistoric Polynesian and Native American populations has long intrigued researchers. Proponents have pointed to the existence of New World crops, such as the sweet potato and bottle gourd, in the Polynesian archaeological record, but nowhere else outside the pre-Columbian Americas1-6, while critics have argued that these botanical dispersals need not have been human mediated7. The Norwegian explorer Thor Heyerdahl controversially suggested that prehistoric South American populations had an important role in the settlement of east Polynesia and particularly of Easter Island (Rapa Nui)2. Several limited molecular genetic studies have reached opposing conclusions, and the possibility continues to be as hotly contested today as it was when first suggested8-12. Here we analyse genome-wide variation in individuals from islands across Polynesia for signs of Native American admixture, analysing 807 individuals from 17 island populations and 15 Pacific coast Native American groups. We find conclusive evidence for prehistoric contact of Polynesian individuals with Native American individuals (around AD 1200) contemporaneous with the settlement of remote Oceania13-15. Our analyses suggest strongly that a single contact event occurred in eastern Polynesia, before the settlement of Rapa Nui, between Polynesian individuals and a Native American group most closely related to the indigenous inhabitants of present-day Colombia.
Assuntos
Fluxo Gênico/genética , Genoma Humano/genética , Migração Humana/história , Indígenas Centro-Americanos/genética , Indígenas Sul-Americanos/genética , Ilhas , Havaiano Nativo ou Outro Ilhéu do Pacífico/genética , América Central/etnologia , Colômbia/etnologia , Europa (Continente)/etnologia , Genética Populacional , História Medieval , Humanos , Polimorfismo de Nucleotídeo Único/genética , Polinésia , América do Sul/etnologia , Fatores de TempoRESUMO
BACKGROUND: Current South American populations trace their origins mainly to three continental ancestries, i.e. European, Amerindian and African. Individual variation in relative proportions of each of these ancestries may be confounded with socio-economic factors due to population stratification. Therefore, ancestry is a potential confounder variable that should be considered in epidemiologic studies and in public health plans. However, there are few studies that have assessed the ancestry of the current admixed Chilean population. This is partly due to the high cost of genome-scale technologies commonly used to estimate ancestry. In this study we have designed a small panel of SNPs to accurately assess ancestry in the largest sampling to date of the Chilean mestizo population (n = 3349) from eight cities. Our panel is also able to distinguish between the two main Amerindian components of Chileans: Aymara from the north and Mapuche from the south. RESULTS: A panel of 150 ancestry-informative markers (AIMs) of SNP type was selected to maximize ancestry informativeness and genome coverage. Of these, 147 were successfully genotyped by KASPar assays in 2843 samples, with an average missing rate of 0.012, and a 0.95 concordance with microarray data. The ancestries estimated with the panel of AIMs had relative high correlations (0.88 for European, 0.91 for Amerindian, 0.70 for Aymara, and 0.68 for Mapuche components) with those obtained with AXIOM LAT1 array. The country's average ancestry was 0.53 ± 0.14 European, 0.04 ± 0.04 African, and 0.42 ± 0.14 Amerindian, disaggregated into 0.18 ± 0.15 Aymara and 0.25 ± 0.13 Mapuche. However, Mapuche ancestry was highest in the south (40.03%) and Aymara in the north (35.61%) as expected from the historical location of these ethnic groups. We make our results available through an online app and demonstrate how it can be used to adjust for ancestry when testing association between incidence of a disease and nongenetic risk factors. CONCLUSIONS: We have conducted the most extensive sampling, across many different cities, of current Chilean population. Ancestry varied significantly by latitude and human development. The panel of AIMs is available to the community for estimating ancestry at low cost in Chileans and other populations with similar ancestry.
Assuntos
Etnicidade/genética , Genética Populacional/organização & administração , Indígenas Sul-Americanos/genética , Polimorfismo de Nucleotídeo Único/genética , Grupos Populacionais/genética , Chile , Feminino , Frequência do Gene/genética , Marcadores Genéticos/genética , Genótipo , Técnicas de Genotipagem , Humanos , Masculino , Filogeografia , SalivaRESUMO
BACKGROUND: Current South American populations trace their origins mainly to three continental ancestries, i.e. European, Amerindian and African. Individual variation in relative proportions of each of these ancestries may be confounded with socio-economic factors due to population stratification. Therefore, ancestry is a potential confounder variable that should be considered in epidemiologic studies and in public health plans. However, there are few studies that have assessed the ancestry of the current admixed Chilean population. This is partly due to the high cost of genome-scale technologies commonly used to estimate ancestry. In this study we have designed a small panel of SNPs to accurately assess ancestry in the largest sampling to date of the Chilean mestizo population (n = 3349) from eight cities. Our panel is also able to distinguish between the two main Amerindian components of Chileans: Aymara from the north and Mapuche from the south. RESULTS: A panel of 150 ancestry-informative markers (AIMs) of SNP type was selected to maximize ancestry informativeness and genome coverage. Of these, 147 were successfully genotyped by KASPar assays in 2843 samples, with an average missing rate of 0.012, and a 0.95 concordance with microarray data. The ancestries estimated with the panel of AIMs had relative high correlations (0.88 for European, 0.91 for Amerindian, 0.70 for Aymara, and 0.68 for Mapuche components) with those obtained with AXIOM LAT1 array. The country's average ancestry was 0.53 ± 0.14 European, 0.04 ± 0.04 African, and 0.42 ± 0.14 Amerindian, disaggregated into 0.18 ± 0.15 Aymara and 0.25 ± 0.13 Mapuche. However, Mapuche ancestry was highest in the south (40.03%) and Aymara in the north (35.61%) as expected from the historical location of these ethnic groups. We make our results available through an online app and demonstrate how it can be used to adjust for ancestry when testing association between incidence of a disease and nongenetic risk factors. CONCLUSIONS: We have conducted the most extensive sampling, across many different cities, of current Chilean population. Ancestry varied significantly by latitude and human development. The panel of AIMs is available to the community for estimating ancestry at low cost in Chileans and other populations with similar ancestry.
Assuntos
Humanos , Masculino , Feminino , Etnicidade/genética , Indígenas Sul-Americanos/genética , Polimorfismo de Nucleotídeo Único/genética , Grupos Populacionais/genética , Genética Populacional/organização & administração , Saliva , Marcadores Genéticos/genética , Chile , Filogeografia , Técnicas de Genotipagem , Frequência do Gene/genética , GenótipoRESUMO
Historical records and genetic analyses indicate that Latin Americans trace their ancestry mainly to the intermixing (admixture) of Native Americans, Europeans and Sub-Saharan Africans. Using novel haplotype-based methods, here we infer sub-continental ancestry in over 6,500 Latin Americans and evaluate the impact of regional ancestry variation on physical appearance. We find that Native American ancestry components in Latin Americans correspond geographically to the present-day genetic structure of Native groups, and that sources of non-Native ancestry, and admixture timings, match documented migratory flows. We also detect South/East Mediterranean ancestry across Latin America, probably stemming mostly from the clandestine colonial migration of Christian converts of non-European origin (Conversos). Furthermore, we find that ancestry related to highland (Central Andean) versus lowland (Mapuche) Natives is associated with variation in facial features, particularly nose morphology, and detect significant differences in allele frequencies between these groups at loci previously associated with nose morphology in this sample.
Assuntos
Migração Humana , Indígenas Norte-Americanos/genética , Indígenas Sul-Americanos/genética , Haplótipos , Humanos , México , Nariz/anatomia & histologia , América do SulRESUMO
Patagonia was the last region of the Americas reached by humans who entered the continent from Siberia â¼15,000-20,000 y ago. Despite recent genomic approaches to reconstruct the continental evolutionary history, regional characterization of ancient and modern genomes remains understudied. Exploring the genomic diversity within Patagonia is not just a valuable strategy to gain a better understanding of the history and diversification of human populations in the southernmost tip of the Americas, but it would also improve the representation of Native American diversity in global databases of human variation. Here, we present genome data from four modern populations from Central Southern Chile and Patagonia (n = 61) and four ancient maritime individuals from Patagonia (â¼1,000 y old). Both the modern and ancient individuals studied in this work have a greater genetic affinity with other modern Native Americans than to any non-American population, showing within South America a clear structure between major geographical regions. Native Patagonian Kawéskar and Yámana showed the highest genetic affinity with the ancient individuals, indicating genetic continuity in the region during the past 1,000 y before present, together with an important agreement between the ethnic affiliation and historical distribution of both groups. Lastly, the ancient maritime individuals were genetically equidistant to a â¼200-y-old terrestrial hunter-gatherer from Tierra del Fuego, which supports a model with an initial separation of a common ancestral group to both maritime populations from a terrestrial population, with a later diversification of the maritime groups.
Assuntos
Variação Genética , Genoma Humano , Indígenas Sul-Americanos/genética , Chile , Feminino , História Antiga , Humanos , Indígenas Sul-Americanos/história , MasculinoRESUMO
OBJECTIVES: Quebrada Camarones, in the Atacama Desert, has the highest arsenic levels in the Americas (>1,000 µg/L). However, the Camarones people have subsisted in this adverse environment during the last 7,000 years and have not presented any epidemiological emergencies. Therefore, to solve this conundrum we compared the frequencies of four protective genetic variants of the AS3MT gene associated with efficient arsenic metabolization, between the living populations of Camarones and two other populations historically exposed to lower levels of arsenic. MATERIALS AND METHODS: The Chilean selected population samples come from Quebrada Camarones (n = 50) and the Azapa Valley (n = 47) in the north and San Juan de la Costa (n = 45) in southern Chile. The genotyping was conducted using PCR-RFLP. We compared the genotypic and allelic frequencies, and estimated the haplotype frequencies in the AS3MT gene. RESULTS: We found higher frequencies of the protective variants in those people from Camarones than in the other two populations. The haplotype estimation showed that the combination of protective variants of CTTA is very frequent in Camarones (68%) and Azapa (48%), but extremely low in San Juan de la Costa (8%). Also, the C variant associated with toxicity risks in the SNP Met287Thr had a lower frequency in Camarones (1%) and is higher in the other populations. DISCUSSION: The higher frequency of protective variants in both northern Chilean populations indicates a long exposure to naturally arsenic-contaminated water sources. Our data suggest that a high arsenic metabolization capacity has been selected as an adaptive mechanism in these populations in order to survive in an arsenic-laden environment.
Assuntos
Adaptação Biológica/genética , Arsênio , Frequência do Gene/genética , Haplótipos/genética , Indígenas Sul-Americanos/genética , Adulto , Antropologia Física , Chile , Estudos Transversais , Feminino , Humanos , Indígenas Sul-Americanos/etnologia , Masculino , Metiltransferases/genética , Pessoa de Meia-Idade , Seleção Genética/genéticaRESUMO
BACKGROUND: Amerindian admixture is an important parameter to consider in epidemiological studies in American countries, to make a proper selection of cases and controls. AIM: To compare Amerindian admixture estimates obtained using ABO*A and ABO*O blood group alleles and ancestral identity markers (AIMs) in the mixed Chilean population. SUBJECTS AND METHODS: Amerindian admixture rates were determined in 720 Chilean volunteers residing in Arica and born in the 15 regions of the country, using ABO*O and ABO*A alleles and 40 AIMs selected from more than 500,000 single nucleotide polymorphisms (SNPs). RESULTS: Mean admixture estimates obtained using ABO*O and ABO*A alleles and AIMs were 35, 47% and 48% respectively. There was concordance in estimates, with the exception of the admixture based on ABO*O allele and AIMs. CONCLUSIONS: In Chile, Amerindian admixture estimates obtained using ABO*A could be used as an alternative to AIMs in justified cases provided the sample size is reasonably large.
Assuntos
Sistema ABO de Grupos Sanguíneos/genética , Indígenas Sul-Americanos/genética , População Branca/genética , Chile/etnologia , Feminino , Frequência do Gene/genética , Marcadores Genéticos/genética , Genética Populacional , Humanos , Masculino , Fenótipo , Polimorfismo de Nucleotídeo Único/genética , Reprodutibilidade dos TestesRESUMO
Background: Amerindian admixture is an important parameter to consider in epidemiological studies in American countries, to make a proper selection of cases and controls. Aim: To compare Amerindian admixture estimates obtained using ABO*A and ABO*O blood group alleles and ancestral identity markers (AIMs) in the mixed Chilean population. Subjects and Methods: Amerindian admixture rates were determined in 720 Chilean volunteers residing in Arica and born in the 15 regions of the country, using ABO*O and ABO*A alleles and 40 AIMs selected from more than 500,000 single nucleotide polymorphisms (SNP´s). Results: Mean admixture estimates obtained using ABO*O and ABO*A alleles and AIM s were 35, 47% and 48% respectively. There was concordance in estimates, with the exception of the admixture based on ABO*O allele and AIMs. Conclusions: In Chile, Amerindian admixture estimates obtained using ABO*A could be used as an alternative to AIMs in justified cases provided the sample size is reasonably large.
Assuntos
Feminino , Humanos , Masculino , Sistema ABO de Grupos Sanguíneos/genética , População Branca/genética , Indígenas Sul-Americanos/genética , Chile/etnologia , Frequência do Gene/genética , Marcadores Genéticos/genética , Genética Populacional , Fenótipo , Polimorfismo de Nucleotídeo Único/genética , Reprodutibilidade dos TestesRESUMO
After several years of research, there is now a consensus that America was populated from Asia through Beringia, probably at the end of the Pleistocene. But many details such as the timing, route(s), and origin of the first settlers remain uncertain. In the last decade genetic evidence has taken on a major role in elucidating the peopling of the Americas. To study the early peopling of South America, we sequenced the control region of mitochondrial DNA from 300 individuals belonging to indigenous populations of Chile and Argentina, and also obtained seven complete mitochondrial DNA sequences. We identified two novel mtDNA monophyletic clades, preliminarily designated B2l and C1b13, which together with the recently described D1g sub-haplogroup have locally high frequencies and are basically restricted to populations from the extreme south of South America. The estimated ages of D1g and B2l, about ~15,000 years BP, together with their similar population dynamics and the high haplotype diversity shown by the networks, suggests that they probably appeared soon after the arrival of the first settlers and agrees with the dating of the earliest archaeological sites in South America (Monte Verde, Chile, 14,500 BP). One further sub-haplogroup, D4h3a5, appears to be restricted to Fuegian-Patagonian populations and reinforces our hypothesis of the continuity of the current Patagonian populations with the initial founders. Our results indicate that the extant native populations inhabiting South Chile and Argentina are a group which had a common origin, and suggest a population break between the extreme south of South America and the more northern part of the continent. Thus the early colonization process was not just an expansion from north to south, but also included movements across the Andes.
Assuntos
DNA Mitocondrial/genética , Emigração e Imigração , Genética Populacional , Haplótipos/genética , Modelos Biológicos , Sequência de Bases , Teorema de Bayes , Etnicidade/genética , Variação Genética , Humanos , Mitocôndrias/genética , Dados de Sequência Molecular , Taxa de Mutação , Conformação de Ácido Nucleico , Filogenia , América do Sul , Fatores de TempoRESUMO
BACKGROUND: Attention deficit/hyperactivity disorder (ADHD) is a common, highly heritable neurobiological disorder of childhood onset, characterized by hyperactivity, impulsiveness or inattentiveness. AIM: To search for differences in risk for ADHD and its components among Chilean native and mixed populations and to look forpossible associations with dopamine receptor D4 (DRD4) and dopamine transporter 1 (DAT1) polymorphisms. MATERIAL AND METHODS: School teachers were requested to complete the Conners test, which uses DSM-IV criteria, to screen for ADHD risk among Aymara and Rapa-Nui students. RESULTS: Rapa-Nui children from Easter Island had the highest risk of hyperactivity/impulsiveness. Aymara children from the Arica-Parinacota Region had lower scores. Although inattentiveness scores had lower differences between groups, overall ADHD score differences among studied populations were highly significant. DRD4 and DAT1 alleles had a heterogeneous distribution. Easter islanders had more divergent frequencies, mostprobably as a result of separate migration routes utilized at different timeperiods during the colonization of America and Polynesia. CONCLUSIONS: The comparison of ADHD risk parameters between Rapa-Nui and Aymara children showed marked differences. Allele distri-bution of dopamine polymorphisms in Easter Island was also significantly different from northern Chile, due probably to different colonization histories. These findings suggest that higher ADHD risk scores in Easter Island children may be linked to the presence of different DRD4 alleles.
Assuntos
Transtorno do Deficit de Atenção com Hiperatividade/genética , Proteínas da Membrana Plasmática de Transporte de Dopamina/genética , Polimorfismo Genético/genética , Receptores de Dopamina D4/genética , Transtorno do Deficit de Atenção com Hiperatividade/etnologia , Estudos de Casos e Controles , Criança , Chile/etnologia , Manual Diagnóstico e Estatístico de Transtornos Mentais , Feminino , Frequência do Gene , Predisposição Genética para Doença , Genótipo , Humanos , Masculino , Fatores de RiscoRESUMO
Background: Attention deficit/hyperactivity disorder (ADHD) is a common, highly heritable neurobiological disorder of childhood onset, characterized by hyperactivity, impulsiveness or inattentiveness. Aim: To search for differences in risk for ADHD and its components among Chilean native and mixed populations and to look forpossible associations with dopamine receptor D4 (DRD4) and dopamine transporter 1 (DAT1) polymorphisms. Material and Methods: School teachers were requested to complete the Conners test, which uses DSM-IV criteria, to screen for ADHD risk among Aymara and Rapa-Nui students. Results: Rapa-Nui children from Easter Island had the highest risk of hyperactivity/impulsiveness. Aymara children from the Arica-Parinacota Region had lower scores. Although inattentiveness scores had lower differences between groups, overall ADHD score differences among studied populations were highly significant. DRD4 and DAT1 alleles had a heterogeneous distribution. Easter islanders had more divergent frequencies, mostprobably as a result of separate migration routes utilized at different timeperiods during the colonization of America and Polynesia. Conclusions: The comparison of ADHD risk parameters between Rapa-Nui and Aymara children showed marked differences. Allele distri-bution of dopamine polymorphisms in Easter Island was also significantly different from northern Chile, due probably to different colonization histories. These findings suggest that higher ADHD risk scores in Easter Island children may be linked to the presence of different DRD4 alleles.
Assuntos
Criança , Feminino , Humanos , Masculino , Transtorno do Deficit de Atenção com Hiperatividade/genética , Proteínas da Membrana Plasmática de Transporte de Dopamina/genética , Polimorfismo Genético/genética , /genética , Transtorno do Deficit de Atenção com Hiperatividade/etnologia , Estudos de Casos e Controles , Chile/etnologia , Manual Diagnóstico e Estatístico de Transtornos Mentais , Frequência do Gene , Predisposição Genética para Doença , Genótipo , Fatores de RiscoRESUMO
In man, infection with South American Andes virus (ANDV) causes hantavirus cardiopulmonary syndrome (HCPS). HCPS due to ANDV is endemic in Southern Chile and much of Argentina and increasing numbers of cases are reported all over South America. A case-fatality rate of about 36% together with the absence of successful antiviral therapies urge the development of a vaccine. Although T-cell responses were shown to be critically involved in immunity to hantaviruses in mouse models, no data are available on the magnitude, specificity and longevity of ANDV-specific memory T-cell responses in patients. Using sets of overlapping peptides in IFN-gamma ELISPOT assays, we herein show in 78 Chilean convalescent patients that Gn-derived epitopes were immunodominant as compared to those from the N- and Gc-proteins. Furthermore, while the relative contribution of the N-specific response significantly declined over time, Gn-specific responses remained readily detectable ex vivo up to 13 years after the acute infection. Tetramer analysis further showed that up to 16.8% of all circulating CD3(+)CD8(+) T cells were specific for the single HLA-B*3501-restricted epitope Gn(465-473) years after the acute infection. Remarkably, Gn(465-473)-specific cells readily secreted IFN-gamma, granzyme B and TNF-alpha but not IL-2 upon stimulation and showed a 'revertant' CD45RA(+)CD27(-)CD28(-)CCR7(-)CD127(-) effector memory phenotype, thereby resembling a phenotype seen in other latent virus infections. Most intriguingly, titers of neutralizing antibodies increased over time in 10/17 individuals months to years after the acute infection and independently of whether they were residents of endemic areas or not. Thus, our data suggest intrinsic, latent antigenic stimulation of Gn-specific T-cells. However, it remains a major task for future studies to proof this hypothesis by determination of viral antigen in convalescent patients. Furthermore, it remains to be seen whether Gn-specific T cells are critical for viral control and protective immunity. If so, Gn-derived immunodominant epitopes could be of high value for future ANDV vaccines.
Assuntos
Antígenos Virais/imunologia , Linfócitos T CD8-Positivos/imunologia , Epitopos de Linfócito T/imunologia , Infecções por Hantavirus/imunologia , Memória Imunológica/imunologia , Anticorpos Antivirais/sangue , Anticorpos Antivirais/imunologia , Separação Celular , Chile , Ensaio de Imunoadsorção Enzimática , Citometria de Fluxo , Orthohantavírus/imunologia , Humanos , Epitopos Imunodominantes/imunologiaRESUMO
A molecular characterization of alleles O1, O1variant (O1v), and the mutation G542A of the ABO blood group was performed in two Amerindian populations of Chile, the Aymara (n = 84) and the Huilliche (n = 75). In addition, a sample of 82 individuals of Santiago belonging to the mixed Chilean population was typed for comparative purposes. The polymorphisms which allow for molecular differentiation of different alleles of the O blood group were studied in genomic DNA. The mutations G188, G261-, G542A, T646A, and C771T, described for alleles O1, O1v, and G542A, were determined using the PCR-RFLP (polymerase chain reaction-restriction fragment length polymorphism) technique. All individuals studied were group O homozygotes for the deletion G261-, which defines the O1 alleles. Results obtained indicate that allele O1v exhibits frequencies of 0.65, 0.81, and 0.60 in Aymara, Huilliche, and Santiago populations, respectively. The frequencies of allele O1(G542A) were 0.119, 0.113, and 0.079 in the same populations. Frequencies for alleles O1 and O1v obtained in the Chilean populations studied concur with the results obtained by other authors, respecting the greater frequency of allele O1v as well as with its heterogeneous distribution in aboriginal South American populations. In Chilean populations, Allele G542A exhibits lower frequencies than those described for indigenous populations from Brazil and may be used as an Amerind admixture marker.
Assuntos
Sistema ABO de Grupos Sanguíneos/genética , Deleção de Genes , Frequência do Gene , Indígenas Sul-Americanos/genética , Polimorfismo de Fragmento de Restrição , Alelos , Chile , Feminino , Heterogeneidade Genética , Humanos , Masculino , Mutação , Reação em Cadeia da PolimeraseRESUMO
We describe subject recruitment from the University of Chile School-Age Children Twin Registry (REMEUCHI). The research aim of REMEUCHI is to quantify the impact of genetic and environmental factors on scholastic achievement in a multicausal approach. The Ministry of Education of Chile, in collaboration with the Registry Office, provided the list of possible twin pairs graduated from high school in 2004 in Chile's metropolitan region. From a population of 70,065 school-age children who had graduated from high school, 434 possible twin pairs were analyzed. Of these, 327 were twins reared together (75.3% of the 434 possible twins pairs) and born between 1986 and 1987 in Chile (mean age 18 years), and approximately 8% were not twins despite matches on full name and birth data. The rest of the possible twin pairs were probably twins reared apart, since one member of the pair had moved to study in another region of Chile. Zygosity was determined through questionnaires, maternal reports of twin similarities, and by the hospital records of the twins at the time of birth. Three hundred and twenty-seven pairs were identified, where monozygotic (MZ) and dizygotic (DZ) twins represented 46.8% and 53.2% of pairs, respectively, with a DZ/MZ ratio of 1.14. Considering same-sex MZ pairs, the percentage of female pairs was greater (55.6%) than male pairs (44.4%). When DZ pairs were analyzed, 47.7% were of opposite sex, 20.1% were male pairs and 32.2% female pairs. In Chile, these findings represent a baseline study to contribute to the establishment of a national twin registry in the future.
Assuntos
Sistema de Registros , Estudos em Gêmeos como Assunto , Adolescente , Chile , Feminino , Humanos , Recém-Nascido , Masculino , Seleção de Pacientes , Gravidez , Sistema de Registros/estatística & dados numéricos , Estudos em Gêmeos como Assunto/estatística & dados numéricos , Gêmeos Dizigóticos , Gêmeos MonozigóticosRESUMO
The genetic variability of four predominantly Indian populations of southern Chile's archipelagos was examined by determining the frequencies of four mitochondrial DNA haplogroups that characterize the American Indian populations. Over 90% of the individuals analyzed presented Native American mtDNA haplogroups. By means of an unweighted group pair method with arithmetic mean (UPGMA) dendrogram, a principal component analysis (PCA) derived from a distance matrix of mtDNA, and the exact test of population differentiation, we are able to prove the existence of a North-South cline. The populations in the northern part of the archipelagos are genetically similar to the Huilliche tribe, while the groups from the South are most closely related to the Fueguino tribe from the extreme South of Chile, and secondarily to the Pehuenche and Mapuche, who are found to the North and East of Chiloé archipelago. These results are consistent with a colonization of the southern archipelagos from Tierra del Fuego. We evaluate the evolutionary relationships of the population of the Chiloé area to groups from other geographic areas of Chile, using analysis of molecular variance (AMOVA). Three Amerindian clusters are identified: one formed by the Aymará and Atacameño, a second by the Huilliche, and a third including the Mapuche, Pehuenche, and Fueguino tribes, and the population inhabiting the South of the Chiloé arcipelago. These groups exhibit a North-South gradient in the frequency of haplogroup B, confirmed by F(ST) tests.
Assuntos
DNA Mitocondrial/genética , Demografia , Evolução Molecular , Variação Genética , Genética Populacional , Indígenas Sul-Americanos/genética , Chile , Análise por Conglomerados , Eletroforese em Gel de Ágar , Geografia , Haplótipos/genética , Humanos , Análise de Componente Principal , Mapeamento por RestriçãoRESUMO
BACKGROUND: There are geographic and ethno historic evidences that relate Paposo cove, located 150 km south of the city of Antofagasta, with old fishermen-collector populations known as Changos, that lived in that zone in the XVII and XVIII centuries. AIM: To perform a genetic and molecular characterization of current Paposo inhabitants, through mitochondrial DNA polymorphism analysis and molecular analysis of classical ABO and Duffy blood groups. MATERIAL AND METHODS: Forty unrelated individuals were studied. The presence of restriction polymorphisms that define A, B, C, and D Amerindian founder mitochondrial haplogroups was studied and molecular determination of classical blood groups were done by PCR. RESULTS: One individual had A haplogroup (2.5%), 19 had B haplogroup (47.5%), six had C haplogroup (15%) and 11 had D haplogrotup (27.5%). Three subjects (7.5%) did not have any of these haplogroups. Among ABO blood groups, the frequency of O101 allele was 0.39, that of allele O201 was 0.53 and that of A allele was 0.08. Duffy blood group frequencies were 0.58 for FY*A and 0.42 for FY*B. FY null allele was not found. CONCLUSIONS: The frequency distribution of Amerindian mitochondrial haplogroups in Paposo inhabitants suggest that these individuals are related with Aymara and Atacameño Amerindians that can be considered culturally and geographically close populations. This proposal is supported by the results of the molecular determination of classical blood groups. Our findings in Paposo cove may represent the distribution of these markers in Chango Indians, of whom there is limited physical evidence and that became extinct near 1890.
Assuntos
Sistema ABO de Grupos Sanguíneos/genética , DNA Mitocondrial/genética , Sistema do Grupo Sanguíneo Duffy/genética , Indígenas Sul-Americanos/genética , Polimorfismo Genético/genética , Chile/etnologia , Frequência do Gene/genética , Marcadores Genéticos/genética , Haplótipos , HumanosRESUMO
BACKGROUND: The analysis of mitochondrial DNA restriction site polymorphisms assigns most Latin American aborgines to four haplogroups. These are characterized by determined polymorphic restriction sites and a deletion of 9 base pairs in the intergenic region V. AIM: To study the distribution of mitochondrial DNA haplogroups in Chilean aboriginal groups, as well as in the mixed population of Santiago. MATERIAL AND METHODS: One hundred twenty Aymara subjects and 23 Atacameño subjects from the Northern part of Chile and 162 randomly chosen subjects residing in Santiago were studied. DNA was extracted from peripheral lymphocytes. Mitochondrial DNA was amplified by means of polymerase chain reaction. RESULTS: The frequency of haplogroup B decreases from north to south. Aymaras in the north have the highest frequency (64%) and it is absent among the Yamanas (previously studied) in the extreme South. Haplogroups C and D show an inverse tendency. It is noteworthy that 84% of mitochondrial haplogroups of the mixed population of Santiago are of Amerindian origin whereas the Y-chromosomes are mainly European. CONCLUSIONS: The peculiar distribution of haplotypes indicate that the population of Santiago is the result of an asymmetric mating system in which the females ancestors were mainly Amerindian and the male ancestors mainly European.