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Pesquisa : G05.045.300 [Categoria DeCS]
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Id: lil-712401
Autor: Octavio-Aguilar, Pablo; Ramos-Frías, Josefina.
Título: Aplicación de la genética de poblaciones en el ámbito de la medicina / Application of population genetics in the field of medicine
Fonte: Biomédica (Bogotá);34(2):171-179, abr.-jun. 2014. tab.
Idioma: es.
Resumo: Las poblaciones humanas obedecen a los mismos supuestos evolutivos que el resto de los organismos, aunque mezclados con elementos sociales y culturales que pueden promover la expresión de ciertas enfermedades en grupos étnicos específicos, causadas principalmente por la frecuente endogamia. En este trabajo se analiza el principio de Hardy-Weinberg desde un enfoque médico, social y biológico, para entender los procesos evolutivos que dan lugar a las enfermedades autosómicas recesivas. A manera de conclusión se puede señalar que la incidencia de estas enfermedades está inversamente relacionada con los niveles de la variabilidad genética en las poblaciones, variabilidad que depende de eventos de colonización, recolonización y migración, así como de convenciones sociales como el racismo, la estratificación social y la segregación.

Human populations follow the same evolutionary principles as other organisms, although mixed with social and cultural elements, which can result in a high prevalence of certain diseases within specific ethnic groups. In this work, the Hardy-Weinberg principle is analyzed from a medical, social and biological viewpoint to understand the evolutionary processes of autosomal recessive diseases. It can be concluded that the incidence of these diseases is inversely related to the levels of genetic variability within populations, which depends on colonization, recolonization and migration events, as well as on social conventions such as racism, social stratification and segregation.
Descritores: Genética Médica/métodos
Genética Populacional/métodos
-Evolução Biológica
Cultura
Frequência do Gene
Interação Gene-Ambiente
Genes Recessivos
Deriva Genética
Predisposição Genética para Doença
Doenças Genéticas Inatas/etnologia
Doenças Genéticas Inatas/genética
Casamento
Modelos Genéticos
Fenótipo
Prevalência
Seleção Genética
Comportamento Social
Limites: Humanos
Tipo de Publ: Research Support, Non-U.S. Gov't
Revisão
Responsável: CO332 - Facultad de Medicina


  2 / 7 LILACS  
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Texto completo SciELO Chile
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Id: lil-683987
Autor: Valenzuela, Carlos Y.
Título: Foundational errors in the Neutral and Nearly-Neutral theories of evolution in relation to the Synthetic Theory: Is a new evolutionary paradigm necessary?
Fonte: Biol. Res;46(2):101-119, 2013. tab.
Idioma: en.
Resumo: The Neutral Theory of Evolution (NTE) proposes mutation and random genetic drift as the most important evolutionary factors. The most conspicuous feature of evolution is the genomic stability during paleontological eras and lack of variation among taxa; 98% or more of nucleotide sites are monomorphic within a species. NTE explains this homology by random fixation of neutral bases and negative selection (purifying selection) that does not contribute either to evolution or polymorphisms. Purifying selection is insufficient to account for this evolutionary feature and the Nearly-Neutral Theory of Evolution (N-NTE) included negative selection with coefficients as low as mutation rate. These NTE and N-NTE propositions are thermodynamically (tendency to random distributions, second law), biotically (recurrent mutation), logically and mathematically (resilient equilibria instead of fixation by drift) untenable. Recurrent forward and backward mutation and random fluctuations of base frequencies alone in a site make life organization and fixations impossible. Drift is not a directional evolutionary factor, but a directional tendency of matter-energy processes (second law) which threatens the biotic organization. Drift cannot drive evolution. In a site, the mutation rates among bases and selection coefficients determine the resilient equilibrium frequency of bases that genetic drift cannot change. The expected neutral random interaction among nucleotides is zero; however, huge interactions and periodicities were found between bases of dinucleotides separated by 1, 2... and more than 1,000 sites. Every base is co-adapted with the whole genome. Neutralists found that neutral evolution is independent of population size (N); thus neutral evolution should be independent of drift, because drift effect is dependent upon N. Also, chromosome size and shape as well as protein size are far from random.
Descritores: Evolução Molecular
Deriva Genética
Mutação/genética
Seleção Genética
-Modelos Genéticos
Filogenia
Densidade Demográfica
Polimorfismo Genético/genética
Tipo de Publ: Revisão
Responsável: CL1.1 - Biblioteca Central


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Texto completo SciELO Chile
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Id: lil-608625
Autor: Valenzuela, Carlos Y.
Título: Heterogeneous periodicity of drosophila mtDNA: new refutations of neutral and nearly neutral evolution
Fonte: Biol. Res;44(3):283-293, 2011. ilus, tab.
Idioma: en.
Resumo: We found a consistent 3-site periodicity of the X²9 values for the heterogeneity of the distribution of the second base in relation to the first base of dinucleotides separated by 0 (contiguous), 1, 2, 3 ... 17 (K) nucleotide sites in Drosophila mtDNA. Triplets of X²9 values were found where the first was over 300 and the second and third ranged between 37 and 114 (previous studies). In this study, the periodicity was significant until separation of 2011K, and a structure of deviations from randomness among dinucleotides was found. The most deviant dinucleotides were G-G, G-C and C-G for the first, second and third element of the triplet, respectively. In these three cases there were more dinucleotides observed than expected. This inter-bases correlation and periodicity may be related to the tertiary structure of circular DNA, like that of prokaryotes and mitochondria, to protect and preserve it. The mtDNA with 19.517 bp was divided into four equal segments of 4.879 bp. The fourth sub-segment presented a very low proportion of G and C, the internucleotide interaction was weaker in this sub-segment and no periodicity was found. The maintenance of this mtDNA structure and organization for millions of generations, in spite of a high recurrent mutation rate, does not support the notion of neutralism or near neutralism. The high level of internucleotide interaction and periodicity indicate that every nucleotide is co-adapted with the residual genome.
Descritores: Sequência de Bases
DNA Mitocondrial/genética
Drosophila/genética
Deriva Genética
Taxa de Mutação
-Sequência de Aminoácidos
Limites: Animais
Responsável: BR1.1 - BIREME


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Texto completo SciELO Chile
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Id: lil-582864
Autor: Valenzuela, Carlos Y.
Título: Internucleotide correlations and nucleotide periodicity in Drosophila mtDNA: New evidence for panselective evolution
Fonte: Biol. Res;43(4):481-486, 2010. tab.
Idioma: en.
Conferência: Apresentado em: Annual Meeting of the Chilean Society of Evolution and the Chilean Society of Genetics, Concepción, October 21-23 2009.
Resumo: Analysis for the homogeneity of the distribution of the second base of dinucleotides in relation to the first, whose bases are separated by 0, 1, 2,... 21 nucleotide sites, was performed with the VIH-1 genome (cDNA), the Drosophila mtDNA, the Drosophila Torso gene and the human p-globin gene. These four DNA segments showed highly significant heterogeneities of base distributions that cannot be accounted for by neutral or nearly neutral evolution or by the "neighbor influence" of nucleotides on mutation rates. High correlations are found in the bases of dinucleotides separated by 0, 1 and more number of sites. A periodicity of three consecutive significance values (measured by the x²9) was found only in Drosophila mtDNA. This periodicity may be due to an unknown structure or organization of mtDNA. This non-random distribution of the two bases of dinucleotides widespread throughout these DNA segments is rather compatible with panselective evolution and generalized internucleotide co-adaptation.
Descritores: DNA Mitocondrial/genética
Drosophila/genética
Deriva Genética
Mutação/genética
Nucleotídeos/genética
-Filogenia
Limites: Animais
Humanos
Responsável: BR1.1 - BIREME


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Texto completo SciELO Cuba
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Id: lil-547078
Autor: Fraga Nodarse, Jorge; Rodríguez Rodriguez, Jinnay; Fuentes González, Omar; Castex Rodriguez, Mayda; Fernández-Calienes Valdés, Aymé.
Título: Variabilidad genética de poblaciones de Triatoma flavida (Hemiptera: Reduviidae) en la península de Guanahacabibes / Genetic variability of Triatoma flavida (Hemiptera: Reduviidae) in Guanahacabibes
Fonte: Rev. cuba. med. trop;61(1), ene.-abr. 2009. ilus, tab, graf.
Idioma: es.
Resumo: La enfermedad de Chagas es una enfermedad transmitida por triatomineos. Triatoma flavida es una especie selvática autóctona de Cuba, que presumiblemente es atraída a las casas por la luz, de las especies encontradas en Cuba es la más abundante. Se investigó la variabilidad genética intrapoblacional e interpoblacional de ejemplares de T. flavida colectados en la región occidental de Cuba, utilizando la técnica del ADN polimórfico amplificado al azar, con la determinación ademßs de posibles relaciones genéticas entre las poblaciones. Un total de 10 cebadores al azar (OPA-1 al 10) fueron usados para evaluar la variabilidad genética dentro de una población y entre 9 poblaciones diferentes de T. flavida, mediante la técnica de ADN polimórfico amplificado al azar. Además, se evaluó la diversidad genética entre individuos salvajes y de la primera generación (F1) obtenidos en el laboratorio, así como entre los diferentes estadios de esta especie. No se detectaron diferencias en los patrones de amplificación del ADN entre los individuos silvestres y de la F1; al igual que entre los diferentes estadios de esta especie. Se encontró homogeneidad genética dentro de la población estudiada y una variabilidad genética baja entre las diferentes poblaciones de T. flavida. Se obtuvieron 2 grupos bien definidos según el análisis del ADN polimórfico amplificado al azar, mostrando concordancia con el origen geográfico, en las poblaciones capturadas en áreas del occidente y el oriente de Guanahacabibes, Pinar del Río. Entre estas poblaciones se encontró una pequeña diferenciación genética (Fst 0,030) y tasas de migración (N> 1) que revelan flujo genético y homogeneidad genética. Los resultados presentados en este estudio establecen una aproximación a la estructura genética de T. flavida. La homogeneidad genética encontrada entre los individuos silvestres de T. flavida constituye un aspecto importante para la implementación de las políticas de control de este vector.

Chagas disease is a Triatomineos-borne disease. Triatoma flavida is an indigenous Cuban species, presumably attracted to houses by light and it is the most abundant species in the country. The intrapopulatinal and interpopulational genetic variability of T. flavida collected in the western region, using the Random Amplified Polymorphic DNA (RAPD) technique, thus determining possible genetic relationships among the populations. A total of ten random primers (OPA-1 at the 10) were used to evaluate the genetic variability in one population and among 9 populations of T. flavida using the RAPD technique. We also evaluate the genetic diversity among wild individuals and their first generation (F1) obtained in the laboratory as well as different stages of this species. Differences were not detected in the amplification patterns among the wild individuals and the F1. The same results were achieved among different life cycles of this species. Genetic homogeneity of the studied population and low genetic variability among different T. flavida populations were observed. Two well-defined groups were obtained according to random amplified polymorphic DNA data; they matched with the geographical origin in the populations captured in areas from east and west of Guanahacabibes, Pinar del Río. Among these populations, small genetic differentiation (Fst 0,030) was found as well as migration rates (N> 1), which reveals the gene flow and genetic homogeneity. The results of this study constitute an approach to the genetic structure of T. flavida. The genetic homogeneity between wild individuals of T. flavida represents an important item for the implementation of the vector control programs.
Descritores: Deriva Genética
Polimorfismo Genético/genética
Triatoma/genética
Responsável: CU1.1 - Biblioteca Médica Nacional


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Texto completo SciELO Brasil
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Id: lil-489839
Autor: Carneiro, P. L. S; Malhado, C. H. M; Affonso, P. R. A. M; Euclydes, R. F; Carneiro, A. P. S; Cunha, E. E; Souza, L. G. R.
Título: Comparação de metodologias de seleção sob oscilação genética / Comparison of selection methodologies under genetic drift
Fonte: Arq. bras. med. vet. zootec;60(4):932-942, ago. 2008. graf.
Idioma: pt.
Resumo: Determinou-se o número adequado de repetições na comparação de métodos de seleção tradicionais e associados a marcadores moleculares, com diferentes tamanhos efetivos e sob diferentes sistemas de acasalamento dos reprodutores selecionados, usando simulação com o programa GENESYS. Para comparar os diferentes métodos de seleção utilizaram-se populações com tamanhos efetivos de 18,18 (TE1) e de 66,66 (TE2) e uma, 10 e 30 repetições por geração, avaliando-se os valores fenotípicos médios. Para as situações com apenas uma repetição, os resultados apresentaram incoerências, independentemente do tamanho efetivo (TE1 ou TE2) ou do sistema de acasalamento (RAA - reprodutores acasalados aleatoriamente, EIC - exclusão de irmãos completos ou EICMI - exclusão de irmãos completos e meio-irmãos). Observou-se que a oscilação genética influencia o ganho genético, principalmente, em populações com pequeno tamanho efetivo e que um valor mínimo de 10 repetições por geração é necessário para assegurar a consistência dos resultados obtidos pelos métodos de seleção.

This work was carried out to determine the required number of replicates for comparison of conventional and molecular marker-associated selection methods in distinct effective population sizes and different mating systems, by simulations using the software GENESYS. Effective populational size of 18.18 (ES1) and 66.66 (ES2), and one, 10, and 30 replicates per generation were used to compare the different selection methods, based on mean phenotypic values. Incongruences results were observed when a single replicate was considered independently of effective size (ES1or ES2) and the mating system (random mating; exclusion of full-sibs or exclusion of both full and half-sibs). Genetic oscillation influenced the genetic gain, mainly in populations of small effective size. Furthermore, at least 10 replicates per generation were required to obtain sound consistent results for both selection methods.
Descritores: Ligação do Par
Deriva Genética
Grupos Populacionais/estatística & dados numéricos
Responsável: BR68.1 - Biblioteca Virginie Buff D'Ápice


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Lôbo, Raysildo Barbosa
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Id: lil-450285
Autor: Vozzi, Pedro Alejandro; Marcondes, Cíntia Righetti; Magnabosco, Cláudio de Ulhôa; Bezerra, Luiz Antonio Framartino; Lôbo, Raysildo Barbosa.
Título: Structure and genetic variability in Nellore (Bos indicus) cattle by pedigree analysis
Fonte: Genet. mol. biol;29(3):482-485, 2006. ilus.
Idioma: en.
Resumo: Parameters based on the probability of gene origin were used to describe the genetic variability in strains of Nellore and polled Nellore (Bos indicus) cattle that participated in the Program for Genetic Improvement of the Nellore Breed (Programa de Melhoramento Genético da Raça Nelore). The effective number of founders was 87.2 for Nellore and 107.9 for polled Nellore, while the number of ancestors was 59.8 for Nellore and 61.5 for polled Nellore and the remaining genomes were 39.4 for Nellore and 34.5 for polled Nellore cattle. The results indicate an intense use (by artificial insemination) of some sires and the absence of subdivisions in the population. The family structure in the two breeds was mainly caused by the genetic contribution of the same sires and only mating preferences for descendants of some founders are recorded in either breed. The results suggest that genetic variability needs monitoring in order to avoid the compromise of genetic improvement in economically important traits in the breeding program.
Descritores: Bovinos/genética
Deriva Genética
Variação Genética
-Linhagem
Limites: Animais
Responsável: BR26.1 - Biblioteca Central



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