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Impact of strong selection for the PrP major gene on genetic variability of four French sheep breeds (Open Access publication)

  • 1Email author,
  • 2,
  • 3,
  • 4,
  • 5,
  • 6, 7,
  • 1,
  • 1,
  • 5,
  • 3,
  • 1 and
  • 6, 7
Genetics Selection Evolution200840:663

  • Received: 7 February 2008
  • Accepted: 22 August 2008
  • Published:


Effective selection on the PrP gene has been implemented since October 2001 in all French sheep breeds. After four years, the ARR "resistant" allele frequency increased by about 35% in young males. The aim of this study was to evaluate the impact of this strong selection on genetic variability. It is focussed on four French sheep breeds and based on the comparison of two groups of 94 animals within each breed: the first group of animals was born before the selection began, and the second, 3–4 years later. Genetic variability was assessed using genealogical and molecular data (29 microsatellite markers). The expected loss of genetic variability on the PrP gene was confirmed. Moreover, among the five markers located in the PrP region, only the three closest ones were affected. The evolution of the number of alleles, heterozygote deficiency within population, expected heterozygosity and the Reynolds distances agreed with the criteria from pedigree and pointed out that neutral genetic variability was not much affected. This trend depended on breed, i.e. on their initial states (population size, PrP frequencies) and on the selection strategies for improving scrapie resistance while carrying out selection for production traits.


  • genetic variability
  • scrapie resistance
  • molecular marker
  • pedigree
  • sheep

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Authors’ Affiliations

INRA, UR631 Station d'Amélioration génétique des animaux, 31326 Castanet-Tolosan, France
Institut de l'É levage, Département de Génétique, 78352 Jouy-en-Josas, France
INRA, UR339 Laboratoire de génétique biochimique et cytogénétique, 78352 Jouy-en-Josas, France
INRA, UR337 Station de génétique quantitative appliquée, 78352 Jouy-en-Josas, France
LABOGENA, 78352 Jouy-en-Josas, France
INRA, UMR1236 Génétique et diversité animales, 78352 Jouy-en-Josas, France
AgroParisTech, UMR1236 Génétique et diversité animales, 75231 Paris 05, France


© INRA, EDP Sciences 2008