Abstract
Prion protein coding gene (PRNP) is the genetic locus correlated with the greatest impact on classical scrapie susceptibility in sheep. At codons 136, 154, and 171 of PRNP alanine/arginine/glutamine (ARQ) and valine/arginine/glutamine (VRQ) haplotypes, in turn, are related to susceptibility to classical scrapie while alaninc/arginine/arginine ARR haplotype is correlated with resistance. The aim of the present study was to genotype the Palestinian native sheep breeds for detection of genetic resistance. A total of 38 healthy sheep from Awassi and Assaf breeds were randomly sampled. Genomic DNA was isolated from blood samples. After PCR amplification and DNA sequencing, ARQ, ARR, ARH, AHQ, ARL and VRQ alleles and ARR/ARQ, ARQ/ARQ, ARQ/ARL, ARH/ARQ, ARH/ARL, AHQ/ARQ and ARQ/VRQ genotypes were detected in PRNP gene. ARQ allele was found as a predominant allele in this study with the frequency of 0.76 for Awassi and Assaf breeds while the uncommon allele ARL was identified at low frequencies in both breeds. In addition, two different polymorphisms were recognized (V121 and L23H) at different codons of PRNP. Results have indicated that most of the genotypes belong to risk group 3. The careful dissemination of ARR/ARR sheep is suggested to increase resistant allele frequencies in Assaf and Awassi breeds.