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The use of selection experiments for detecting quantitative trait loci

Published online by Cambridge University Press:  01 June 1997

L. OLLIVIER
Affiliation:
INRA-Station de génétique quantitative et appliquée, 78352 Jouy-en-Josas Cedex, France
L. A. MESSER
Affiliation:
Department of Animal Science, Iowa State University, Ames, IA 50011, USA
M. F. ROTHSCHILD
Affiliation:
Department of Animal Science, Iowa State University, Ames, IA 50011, USA
C. LEGAULT
Affiliation:
INRA-Station de génétique quantitative et appliquée, 78352 Jouy-en-Josas Cedex, France

Abstract

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Gene frequency changes following selection may reveal the existence of gene effects on the trait selected. Loci for the selected quantitative trait (SQTL) may thus be detected. Additionally, one can estimate the average effect (α) of a marker allele associated with an SQTL from the allele frequency change (Δq) due to selection of given intensity (i). In a sample of unrelated individuals, it is optimal to select the upper and lower 27% for generating Δq in order to estimate α. For a given number of individuals genotyped, this estimator is 0·25i2 times more efficient than the classical estimator of α, based on the regression of the trait on the genotype at the marker locus. The method is extended to selection criteria using information from relatives, showing that combined selection considerably increases the efficiency of estimation for traits of low heritability. The method has been applied to the detection of SQTL in a selection experiment in which the trait selected was pig litter size averaged over the first four parities, with i=3. Results for four genes are provided, one of which yielded a highly significant effect. The conditions required for valid application of the method are discussed, including selection experiments over several generations. Additional advantages of the method can be anticipated from determining gene frequencies on pooled samples of blood or DNA.

Type
Research Article
Copyright
© 1997 Cambridge University Press