Diversidade em populações simuladas com base em locos multialélicos

• Ano de defesa: 2007
• Autor(a) principal: Ferreira, Fábio Medeiros
• Orientador(a): Cruz, Cosme Damião
• Banca de defesa: Furtado, Marcos Ribeiro , Waldschmidt, Ana Maria
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Viçosa
• Programa de Pós-Graduação: Doutorado em Genética e Melhoramento
• Departamento: Genética animal; Genética molecular e de microrganismos; Genética quantitativa; Genética vegetal; Me
• País: BR
• Palavras-chave em Português: Diversidade genética; Marcadores moleculares; Melhoramento genético
• Palavras-chave em Inglês: Genetic diversity; Molecular markers; Genetic improvement
• Área do conhecimento CNPq: CNPQ::CIENCIAS BIOLOGICAS::GENETICA::GENETICA QUANTITATIVA
• Link de acesso: http://locus.ufv.br/handle/123456789/1412

The availability of the new theoretical and practical referential systems has been welcome and important as a guide to using softwares and biometric methods, since it makes possible a better use of the data file and the correct interpretation of the results. So, the following simulations were accomplished: base-populations subjected to either randomly mating and selfings; formation of hybrid populations F1; segregant generations Fn and backcrossing generations provided with information from twenty codominant and multiallelic loci. Several biometric analyses were applied at intra- and inter-populational levels, by using seven computer programs that were gratuitously available in internet. The objectives were: i) to evaluate the genetic diversity either between and within populations; ii) to compare the applied methodologies; iii) to verify both potentiality and functionality of the computer programs; and iv) to help the researchers either in using several biometric methods for the genetic data analysis and in accomplishing the analyses through the programs. The following measures were distinguished as optimum descriptors of the intra populational: the allele effective numbers (Ae); polymorphic information content (PIC); Shannon-Wiener index (H'); observed heterozygosity (Ho); fixation/endogamy index (f); and expected heterozygosity (He or j D ), as optimum descriptors of the intra-populational genetic diversity. For a high sample size (Ni = 200), the different estimators of the endogamy/fixation coefficient slightly differed concerning to their estimates, as well as for the biased and non-biased expected heterozygosity. Because the effective-sized values (Ne) were inversely proportional to the endogamy coefficient, they revealed selfings to provide lower Ne. The populations under random mating showed values Ne =~ Ni, since they fulfill the presuppositions of an idealized population with random matings. Those populations under selfing such as the segregant generations Fn were unanimous concerning to disequilibrium inside their loci. The disequilibrium in the hybrid population loci occurs for those where there are no different allelic frequencies between crossed populations. The hybridization process in the backcrossing populations can or cannot lead one locus to Hardy-Weinberg equilibrium (HWE), what will depend from both genic and genotypic combinations between the hybrid F1 or the antecedent backcrossing generation with the recurrent genitor. Deviations in the HWE proportions are useful to the definition of alternative hypotheses concerning to either excess or deficiency of heterozygotes. The tests of qui-square, likelihood ratio, and the exact test with permutations were in accordance for the HWE detection or not. As the random mating advances, there is a tendency to reach the gametic equilibrium and the disequilibrium coefficient to be decreased. The qui-square tests 2 χ and likelihood ratio (G2) were in concordance in relation to the detection or non-detection of the gametic disequilibrium. In general, the distance measures used in the interpopulational diversity study rather composed very similar groups, when applying the clustering methods by Tocher, UPGMA and two-dimensional projection (2D). Though, the distance measures with similar philosophies and under some situations provided identical groupings, such as the distances: the mean Euclidian (DE) and Roger (DR); Latter (1972 and 1973) (DL72 and DL73) and Reynolds (D`RWC); modified Rogers (DGS), minimum (Dm) and Reynolds (DRWC); as well as the cosine complement (DCOS), cord length (DCC) and Nei et al. (1983) (DN83). Comparisons at genotypic level, such as the Hedrick genotypic distance (DH) provide additional information at which the gene distances probably cannot promote. The geometric distance measures (DE, DR, DGS, DCOS and DCC) showed higher efficiency in graphic projection. It was verified that as the backcrossing generations advanced, the recovery of the recurrent parental genome really occurs, which is reflected on higher genetic differentiation between the backcrossing population and the donor genitor. The variance analysis of the allelic frequencies promoted an equal partition of either individual variations within populations and genes within individuals, whereas the molecular variance analysis (AMOVA) ascribed great part of the variation to the genes within individuals. The variation among populations and the sum of the variation within populations and within individuals were identically quantified by the allelic frequencies and Nei methods. The values of the statistics F were equal, based on the allelic frequency variance analysis and AMOVA. The analysis by statistics F allowed to understand how the variation is distributed between parental populations and segregant generations. The programs under study showed to be appropriate for the study of the genetic diversity in populations with multiallelic loci. The programs GENES and PowerMarker are distinguished as a function of the several analysis methods directed to this study. The simulated study made possible to accomplishing satisfactory comparisons among either the available methodologies and the computer programs, therefore constituting a theoretical referential that can help the researchers to draw inferences on the populational genetics.