TAILIEUCHUNG - Báo cáo sinh học: "An approximate theory of selection assuming a finite number of quantitative trait loci"

Tuyển tập các báo cáo nghiên cứu về sinh học được đăng trên tạp chí sinh học Journal of Biology đề tài: An approximate theory of selection assuming a finite number of quantitative trait loci | 379 Genet Sei Evol 1994 26 379-400 Elsevier INRA Original article An approximate theory of selection assuming a finite number of quantitative trait loci c Chevalet Institut National de la Recherche Agronomique Centre de Recherches de Toulouse Laboratoire de Génétique Cellulaire BP 27 31326 Castanet-Tolosan cedex France Received 24 August 1993 accepted 11 May 1994 Summary - An approximate theory of mid-term selection for a quantitative trait is developed for the case when a finite number of unlinked loci contribute to phenotypes. Assuming Gaussian distributions of phenotypic and genetic effects the analysis shows that the dynamics of the response to selection is defined by one single additional parameter the effective number Le of quantitative trait loci QTL . This number is expected to be rather small 3-20 if QTLs have variable contributions to the genetic variance. As is confirmed by simulation the change with time of the genetic variance and of the cumulative response to selection depend on this effective number of QTLs rather than on the total number of contributing loci. The model extends the analysis of Bulmer and shows that an equilibrium structure arises after a few generations in which some amount of genetic variability is hidden by gametic disequilibria. The additive genetic variance 1 4 and the genic variance va remain linked by V4 va k 1 l Le i2Vx where K is the proportion of variance removed by selection and h2 the current heritability of the trait. From this property a complete approximate theory of selection can be developed and modifications of correlations between relatives can be proposed. However the model generally overestimates the cumulative response to selection except in early generations which defines the time scale for which the present theory is of potential practical value. quantitative genetics selection genetic variance Resume Théorie approchée de la selection pour un caractère dũ à un nombre flni de locus. Une théorie approchée de la .

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