De Vries F, Hamann H, Distl O
Institut für Tierzucht und Vererbungsforschung, Stiftung Tierärztliche Hochschule Hannover.
Dtsch Tierarztl Wochenschr. 2006 Feb;113(2):43-50.
Scrapie resistance is related to polymorphisms of the prion protein (PrP) gene. The homozygous ARR/ARR genotype of the prion protein gene is associated with high resistance against conventional scrapie infections. But this can lead to a distinct loss of genetic variation in breeds with a small population size or a low frequency of the ARR allele. For these populations an optimal breeding scheme for breeding towards scrapie resistance and an arbitrarily chosen production trait with conservation of the genetic diversity is not known yet. A simulation programme was developed, in which the structures of local populations could be used as input parameters, and the development of the ARR allele frequency, of the inbreeding coefficient, of a production trait and the genetic drift were computed in dependence of different selection schemes for scrapie resistance. An optimal strategy for the German Grey Heath population from Lower Saxony should be found. An optimal strategy in a breeding programme for ARR homozygosis should also maintain the genetic diversity present in a breed. This could be achieved when initially ARR heterozygous sheep were bred until a certain threshold value of the ARR allele was reached. The speed and costs of the breeding progress towards fixation of the ARR allele should then be optimized with regard to the aims of the breeders and breeding organisations, whereas a faster breeding towards scrapie resistance goes along with higher genotyping costs and vice versa.
抗瘙痒病能力与朊病毒蛋白（PrP）基因的多态性有关。朊病毒蛋白基因的纯合ARR/ARR基因型与对传统瘙痒病感染的高抗性相关。但这可能导致种群规模较小或ARR等位基因频率较低的品种遗传变异明显丧失。对于这些种群，尚未知晓一种针对抗瘙痒病育种以及在保留遗传多样性的情况下任意选择生产性状的最优育种方案。开发了一个模拟程序，其中可以将当地种群结构用作输入参数，并根据不同的抗瘙痒病选择方案计算ARR等位基因频率、近亲繁殖系数、生产性状以及遗传漂变的发展情况。应找到下萨克森州德国灰石南种群的最优策略。ARR纯合子育种计划中的最优策略还应保持品种中现有的遗传多样性。当初始培育ARR杂合绵羊直至达到ARR等位基因的某个阈值时，便可实现这一点。然后应根据育种者和育种组织的目标，优化朝着ARR等位基因固定方向的育种进展速度和成本，而朝着抗瘙痒病方向更快的育种会伴随着更高的基因分型成本，反之亦然。
