Impact of strong selection for the <it>PrP </it>major gene on genetic variability of four French sheep breeds (<it>Open Access publication</it>)
2008
Pantano Thais | Cribiu Edmond | Leymarie Cyril | Neuts Étienne | Bed'hom Bertrand | Amigues Yves | Laloë Denis | Moazami-Goudarzi Katayoun | Brochard Mickaël | Palhiere Isabelle | Bibé Bernard | Verrier Étienne
<p>Abstract</p> <p>Effective selection on the <it>PrP </it>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 <it>PrP </it>gene was confirmed. Moreover, among the five markers located in the <it>PrP </it>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, <it>i.e. </it>on their initial states (population size, <it>PrP </it>frequencies) and on the selection strategies for improving scrapie resistance while carrying out selection for production traits.</p>
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