Theoretical and Applied Genetics

, Volume 93, Issue 1, pp 71-80

First online:

Methods for multiple-marker mapping of quantitative trait loci in half-sib populations

  • S. A. KnottAffiliated withINRA Station de Génétique Quantitative et Appliquée
  • , J. M. ElsenAffiliated withINRA Station d'Amélioration Génétique des Animaux
  • , C. S. HaleyAffiliated withINRA Station de Génétique Quantitative et Appliquée

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In this paper we consider the detection of individual loci controlling quantitative traits of interest (quantitative trait loci or QTLs) in the large half-sib family structure found in some species. Two simple approaches using multiple markers are proposed, one using least squares and the other maximum likelihood. These methods are intended to provide a relatively fast screening of the entire genome to pinpoint regions of interest for further investigation. They are compared with a more traditional single-marker least-squares approach. The use of multiple markers is shown to increase power and has the advantage of providing an estimate for the location of the QTL. The maximum-likelihood and the least-squares approaches using multiple markers give similar power and estimates for the QTL location, although the likelihood approach also provides estimates of the QTL effect and sire heterozygote frequency. A number of assumptions have been made in order to make the likelihood calculations feasible, however, and computationally it is still more demanding than the least-squares approach. The least-squares approach using multiple markers provides a fast method that can easily be extended to include additional effects.

Key words

QTL mapping Genetic mapping Animal breeding Half-sibs