Genetics, Vol. 161, 1625-1632, August 2002, Copyright © 2002

Exploring Alternative Models for Sex-Linked Quantitative Trait Loci in Outbred Populations: Application to an Iberian x Landrace Pig Intercross

Miguel Pérez-Encisoa,b, Alex Clopc, Josep M. Folchc, Armand Sánchezc, Maria A. Oliverd, Cristina Óviloe, C. Barragáne, Luis Varonaa, and José L. Nogueraa
a Centre UdL-IRTA, Area de Producció Animal, 25198 Lleida, Spain,
b INRA, Station d'Amélioration Génétique des Animaux, BP 27, 31326 Castanet-Tolosan, France,
c Universitat Autònoma de Barcelona, Facultat de Veterinaria, Unitat de Genètica i Millora, 08193 Bellaterra, Spain,
d IRTA, Centre de Tecnologia de la Carn, 17121 Monells, Girona, Spain
e SGIT-INIA, Area de Mejora Genética Animal, 28040 Madrid, Spain

Corresponding author: Miguel Pérez-Enciso, Station d'Amélioration Génétique des Animaux, BP27, 31326 Castanet-Tolosan, France., mperez{at}toulouse.inra.fr (E-mail)

Communicating editor: C. HALEY

We present a very flexible method that allows us to analyze X-linked quantitative trait loci (QTL) in crosses between outbred lines. The dosage compensation phenomenon is modeled explicitly in an identity-by-descent approach. A variety of models can be fitted, ranging from considering alternative fixed alleles within the founder breeds to a model where the only genetic variation is within breeds, as well as mixed models. Different genetic variances within each founder breed can be estimated. We illustrate the method with data from an F2 cross between Iberian x Landrace pigs for intramuscular fat content and meat color component a*. The Iberian allele exhibited a strong overdominant effect for intramuscular fat in females. There was also limited evidence of one or more regions affecting color component a*. The analysis suggested that the QTL alleles were fixed in the Iberian founders, whereas there was some evidence of segregation in Landrace for the QTL affecting a* color component.




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