Tuyển tập các báo cáo nghiên cứu về sinh học được đăng trên tạp chí sinh học Journal of Biology đề tài: Mapping linked quantitative trait loci via residual maximum likelihood | 14 JANV. 1998 Genet Sei Evol 1997 29 529-544 Elsevier Inra 529 Original article Mapping linked quantitative trait loci via residual maximum likelihood FE Grignola Q Zhang I Hoeschele Department of Dairy Science Virginia Polytechnic Institute and State University Blacksburg VA 24061-0315 USA Received 2 September 1996 accepted 19 August 1997 Summary - A residual maximum likelihood method is presented for estimation of the positions and variance contributions of two linked QTLs. The method also provides tests for zero versus one QTL linked to a group of markers and for one versus two QTLs linked. A deterministic derivative-free algorithm is employed. The variance-covariance matrix of the allelic effects at each QTL and its inverse is computed conditional on incomplete information from multiple linked markers. Covariances between effects at different QTLs and between QTLs and polygenic effects are assumed to be zero. A simulation study was performed to investigate parameter estimation and likelihood ratio tests. The design was a granddaughter design with 2 000 sons 20 sires of sons and nine ancestors of sires. Data were simulated under a normal-effects and a biallelic model for variation at each QTL. Genotypes at five or nine equally spaced markers were generated for all sons and their ancestors. Two linked QTLs accounted jointly for 50 or 25 of the additive genetic variance and distance between QTLs varied from 20 to 40 cM. Power of detecting a second QTL exceeded all the time for the 50 QTLs and when the distance was at least 30 cM for the 25 QTLs. An intersection-union test is preferred over a likelihood ratio test which was found to be rather conservative. Parameters were estimated quite accurately except for a slight overestimation of the distance between two close QTLs. quantitative trait loci multipoint mapping residual maximum likelihood outcross population Resume Detection de genes lies à effets quantitatifs QTL grace au maximum de vraisemblance .
