Hotel Estoril Eden, Monte Estoril,
5-8 October 2005



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apping of Quantitative Phenotype Using the Allelic Penetrance Framework

Elisabete Barata Fernandes1, Luísa Canto e Castro Loura1 and Carlos Penha Gonçalves2
DEIO e CEA, Faculdade de Ciências, Universidade de Lisboa, Portugal
Instituto Gulbenkian de Ciência, Portugal

The statistical problem of localization of quantitative trait loci (QTLs) has come to deserve great attention in the last decades. Single marker analysis and interval mapping using the likelihood approach have been the most commonly used methods for QTLs mapping in experimental crosses. These methods assume that one quantitative phenotype follows a normal distribution in the population. In this paper we propose a new methodology of mapping of QTLs based the allelic penetrance approach, previously described for the modulation of binary phenotype, but now extended for the quantitative traits. In our framework, the conditional distribution of phenotype given the genotype is represented by a mixture of normal distributions, with weights defined by the probabilities of phenotypic expression of the alleles composing the genotype. This method has the advantage to have higher precision in the localization of QTLs when the distribution of phenotype is not normal. For illustrative purposes we fit this model to data sets and the results are compared with produced for the traditional methods of mapping of QTLs.

Keywords: quantitative trait loci, allelic penetrance approach