Tuyển tập các báo cáo nghiên cứu về sinh học được đăng trên tạp chí sinh học Journal of Biology đề tài: Estimation of covariance components between one continuous and one binary trait | 303 Genet. Sei. Evol. 1989 21 303-315 Elsevier INRA Original article Estimation of covariance components between one continuous and one binary trait H. Simianer1 and . Schaeffer2 1 Liebig University Department of Animal Breeding and Genetics Bismarckstr. 16 D-6300 Giessen FRG 2 University of Guelph Department of Animal and Poultry Science Guelph Ontario NIG 2W1 Canada received 17 December 1987 accepted 14 October 1988 Summary - A method is described to estimate variance and covariance components in a multiple trait situation with one continuous and one binary trait. An underlying bivariate normal distribution is assumed with one variable dichotomized on the observable scale through a fixed threshold. A mixed linear model is applied to the underlying scale and Bayesian arguments are employed to derive estimation procedures for both location and dispersion parameters. This leads to a nonlinear system of equations similar to the mixed model equations for observations that have been transformed by a Cholesky decomposition of the residual variance-covariance matrix so that the residual covariance between the two transformed traits is zero thereby simplifying construction of the multiple trait mixed model equations. The procedures for estimating genetic variances and covariances and the residual variance for the continuous trait are equivalent to restricted maximum likelihood in the multivariate normal case. The residual correlation is estimated using a maximum likelihood approach. Suitable computing strategies are indicated and a simulation study is given to illustrate the use of the method The impact of small subclass size on the estimates is seen to be a serious drawbackto the proposed method. Possible generalizations of the method and potential problems in its practical application are discussed. variance covariance estimation binary trait methods Resume - Estimation des composantes de la covariance entre un caractère continu et un caractère binaire. On décrit une
