RESUMO
Classical selection for increasing prolificacy in sheep leads to a concomitant increase in its variability, even though the objective of the breeder is to maximise the frequency of an intermediate litter size rather than the frequency of high litter sizes. For instance, in the Lacaune sheep breed raised in semi-intensive conditions, ewes lambing twins represent the economic optimum. Data for this breed, obtained from the national recording scheme, were analysed. Variance components were estimated in an infinitesimal model involving genes controlling the mean level as well as its environmental variability. Large heritability was found for the mean prolificacy, but a high potential for increasing the percentage of twins at lambing while reducing the environmental variability of prolificacy is also suspected. Quantification of the response to such a canalising selection was achieved.
Assuntos
Variação Genética , Tamanho da Ninhada de Vivíparos/genética , Modelos Genéticos , Valor Preditivo dos Testes , Característica Quantitativa Herdável , Animais , Teorema de Bayes , Simulação por Computador , Coleta de Dados , Feminino , Matemática , Método de Monte Carlo , Gravidez , Seleção Genética , Ovinos/genética , GêmeosRESUMO
MOTIVATION: Quick and easy gene mapping by the use of a panel of cytogenetically characterized somatic cell hybrids is possible, even if some discordant experimental results arise. RESULTS: An interactive program is proposed and is made available on a WWW site to users of a somatic cell hybrid panel. Assignments to chromosomes and subchromosomal regions are based on likelihood calculations and Bayes' theorem, and a confidence level is provided. The method is illustrated in the case of the pig genome.
