TAILIEUCHUNG - Báo cáo sinh học: "Phenotypic plasticity of body pigmentation in Drosophila: Computing marginal posterior densities of genetic parameters of a multiple trait animal model using Laplace approximation or Gibbs sampling"

Tuyển tập các báo cáo nghiên cứu về sinh học được đăng trên tạp chí sinh Original cung cấp cho các bạn kiến thức về sinh học đề tài:Phenotypic plasticity of body pigmentation in Drosophila: Computing marginal posterior densities of genetic parameters of a multiple trait animal model using Laplace approximation or Gibbs sampling. | Genet Sei Evol 1997 29 427-450 @ Elsevier Inra 427 Original article Computing marginal posterior densities of genetic parameters of a multiple trait animal model using Laplace approximation or Gibbs sampling A Hofer V Ducrocq Station de génétique quantitative et appliquée Institut national de la recherche agronomique 78352 Jouy-en-Josas cedex France Received 3 March 1997 accepted 14 August 1997 Summary - Two procedures for computing the marginal posterior density of heritabilities or genetic correlations ie Laplace s method to approximate integrals and Gibbs sampling are compared. A multiple trait animal model is considered with one random effect no missing observations and identical models for all traits. The Laplace approximation consists in computing the marginal posterior density for different values of the parameter of interest. This approximation requires the repeated evaluation of traces and determinants which are easy to compute once the eigenvalues of a matrix of dimension equal to the number of animals are determined. These eigenvalues can be efficiently computed by the Lanczos algorithm. The Gibbs sampler generates samples from the joint posterior density. These samples are used to estimate the marginal posterior density which is exact up to a Monte-Carlo error. Both procedures were applied to a data set with semen production traits of 1957 Normande bulls. The traits analyzed were volume of the ejaculate motility score and spermatozoa concentration. The Laplace approximation yielded very accurate approximations of the marginal posterior density for all parameters with much lower computing costs. marginal posterior density Laplace approximation Lanczos method Gibbs sampling I genetic parameters Resume - Calcul des densités marginales a posteriori des paramètres génétiques d un modèle animal multicaractère en utilisant une approximation laplacienne OU réchantillonnage de Gibbs. Deux procedures de calcul de la densité marginale a posteriori des .

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