GENETIC STRUCTURE AT THE PRION PROTEIN LOCUS (PrP) OF BOTOSANI KARAKUL SHEEP POPULATIONS IN RELATION TO THE ACCURACY AND INTENSITY OF SELECTION MECHANISMS
Gh. Hrincă, S.E. Georgescu, G. Vicovan, I. Nechifor
Abstract
The paper investigates the fixing degree of alleles at the PrP locus in the Botosani Karakul sheep bred in two farm types: elite farm (with very rigorous selection criteria) and production farms (with lower selection exigencies). Sheep genotyping at PrP locus was performed by the Real-Time PCR technique. Significant differences were noted between the two farm types concerning the genetic structure at this locus. In sheep belonging to private farms, all five prion alleles are found: ARR, AHQ, ARH, ARQ and VRQ. In sheep of elite farm, four alleles are present, the allele VRQ lacking. This situation leads to a more emphasized polymorphism at the PrP locus in sheep of private farms revealed by expressing of 11 prion genotypes in comparison with the seven ones found in sheep of elite farm. In the elite farm, the ARR allele (associated with increased resistance to scrapie) is more frequent, causing higher incidences of genotypes containing this allele than in the private farms. Although the VRQ allele (associated with high susceptibility to develop the prion disease) is sporadically spread in private farms, it contributes to expressing of two genotypes. The ARQ allele (with a middle association level regarding the resistance / susceptibility to scrapie) is frequently found in both farm types (especially in homozygous status), but it is more common in the production farms. The elite farm is in genetic disequilibrium PrP, and the production farms conform to the Hardy-Weinberg law at this locus.
