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Access the genetic variability of endangered and isolated populations has become an important conservation tool. Astyanax scabripinnis is a well-known fish model for genetic studies, forming very isolated populations in headwaters. Besides that, this species frequently presents supernumerary chromosomes, which elevates the interest on genetic studies. Genetic diversity of an Astyanax scabripinnispopulation from the Atlantic Forest (Serra da Mantiqueira region, Brazil) was assessed with microsatellite markers for the first time. Since microsatellite markers are not described for this species, we tested markers described for a related species for transferability to A. scabripinnis. Six polymorphic loci were sufficiently reliable for population genetic analysis. We found that this population passed through a recent bottleneck because of the presence of an excess of heterozygotes, low allelic diversity, heterozygosity excess, and small effective population size. Individuals with and without B chromosomes were previously identified in this population and our study found private alleles in the individuals without B chromosomes. Furthermore, when individuals without B chromosomes were removed from the analysis, the population did not present heterozygosity excess, suggesting that the bottleneck event was driven by individuals with B chromosomes. Our results provide an insight into the value of microsatellite markers as molecular tools and is the first genetic study using molecular data of A. scabripinnis from this area.
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Characidae/genética , Repeticiones de Microsatélite , Variación GenéticaRESUMEN
Aim: This study aimed to uncover the diversity and population structure of 128 sesame genotypes using ISSR markers and identify highly diverse genotypes for the purposes of broadening the genetic base of sesame landraces grown in Ethiopia. Place and Duration of Study: The study was conducted in Botany research laboratory of Kasetsart University, Thailand, from April to July, 2013. Methodology: Genomic DNA of 128 sesame genotypes were subjected to PCR amplification and electrophoresis using seven ISSR markers and a binary data matrix prepared for each primer by scoring clear bands. The data generated were used to calculate the number of total bands (TB), polymorphic bands (PB), polymorphism percentage (P %) and polymorphic information content (PIC) for each locus. The number of different (Na) and effective (Ne) alleles, polymorphic loci (%), Shannon’s information index (I) and Nei’s gene diversity (He) for each population were calculated using GenAlEx 6.5 software. The data were also subjected to analysis of molecular variance (AMOVA) and principal coordinate analysis (PCoA) via distance matrix. Fixation index (Fst) was computed to measure genetic differentiation among populations. Genetic associations among individual genotypes were determined based on dissimilarity matrix using Darwin version 5.0 and a Neighbour-Joining hierarchal tree was constructed based on UPGMA. Results: The 7 ISSR primers in 128 sesame genotypes yielded 96 reproducible amplified bands. The number of amplified bands varied from 7 to 19. Out of 96 bands, 89 (92.2%) were polymorphic. Average number of bands and polymorphic bands per primer were 14 and 12.6 respectively. The polymorphic information content (PIC) value ranged between 0.26 and 0.76, showing the high informativeness of the selected primers. The overall gene diversity and Shannon’s information index were 0.37 and 0.54 respectively. Average dissimilarity value among the genotypes was 0.39. Maximum dissimilarity (0.88) was observed between genotypes Amr-NW6 and Amr-NG9 and less dissimilarity (0.014) was recorded between Amr-NW1 and Amr-NG1. SNNP-7 was the most diverse of all genotypes with highest average dissimilarity value of 0.77. AMOVA showed lower genetic divergence between populations (6%) than within population (94%) with average Fst of 0.061 across populations. The high intra-population variation could be because of large number of genotypes included and due to high out-crossing nature of sesame. Clustering and PCoA analyses clustered the genotypes into individual groups where most of the landraces were grouped in separate clusters irrespective of their geographic origins, while the cultivars were grouped in one cluster, suggesting less variability within the released varieties than the landraces. Accessions no. 56, 73, and 105 were out grouped from the rest. Conclusion: There exist considerable variations among sesame genotypes collected from different geographical regions of Ethiopia. Genotypes Amr-NSh-6, Benishangul-6 and SNNP-7 exhibited a good amount of genetic divergence and hence can be used in crossing program for genetic improvement of sesame in Ethiopia.
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Introducción: el sistema sanguíneo ABO es un factor de riesgo para la malaria. Esta asociación afecta la estructura genética de poblaciones donde la malaria es endémica. Se desconoce la estructura genética para el sistema ABO en pacientes de Gambia. Objetivo: caracterizar la estructura genética para el sistema ABO de la población gambiana. Métodos: se realizó un estudio transversal en una muestra de 739 individuos admitidos en el Hospital Docente Reina Victoria, Gambia, desde diciembre de 2011 hasta septiembre de 2012. Los grupos del sistema ABO fueron determinados con el uso de antisueros comerciales. Los datos fueron digitalizados en forma de archivos Excel y procesados con el software SPSS y GDA. Resultados: las frecuencias para la grupos A, AB, B y O fueron: 0,24; 0,06; 0,22 y 0,48, respectivamente. Se asumió un equilibrio de Hardy-Weinberg, las frecuencias alélicas estimadas fueron de 0,16; 0,15 y 0,69 para los alelos I A, I B e I O, respectivamente. Esta distribución no mostró desviación significativa del equilibrio genético (p=0,9978). La heterocigocidad observada (H O=0,4804) mostró un ligero incremento respecto a la esperada (H E=0,4796). El mayor valor para el índice de fijación global correspondió al alelo I O (F ST=-0,002594). Conclusiones: existió un ligero incremento en la diversidad genética para el sistema ABO en pacientes de Gambia, que favoreció la transmisión del alelo I O y que sugirió la ocurrencia de cambios micro-evolutivos en respuesta a la presión selectiva impuesta por la malaria endémica, que significó el grupo O protector frente a la infección por el Plasmodium falciparum.
Introduction: the ABO blood system is a risk factor for malaria. This association affects the genetic structure of populations where malaria is endemic. Genetic structure for the ABO system in Gambia is unknown. Objective: to characterize the genetic structure for the ABO system of the Gambian population. Methods: a cross-sectional study was performed in a sample of 739 individuals admitted to the Reina Victoria Teaching Hospital , Gambia , from December 2011 to September 2012. ABO groups were determined using commercial antiserum The data were digitized in the form of Excel files and processed with SPSS software and GDA. Results: frequencies for groups A, AB, B and O were 0.24, 0.06, 0.22 and 0.48, respectively. A balance of Hardy -Weinberg equilibrium was assumed, estimated allele frequencies were 0.16, 0.15 and 0.69 for I A, I B and I O, respectively alleles. This distribution showed no significant deviation from genetic equilibrium (p = 0.9978). The observed heterozygosity (H O = 0.4804) showed a slight increase from the expected one (H E = 0.4796). The highest value for the overall index corresponded to first allele fixation (F ST = -0.002594). Conclusions: there was a slight increase in genetic diversity for the ABO system in Gambia, favoring transmission first allele and suggested the occurrence of micro - evolution changes in response to selective pressure imposed by endemic malaria, which represented the group O protector against infection by Plasmodium falciparum.