Prions are considered the only agents of transmissible spongiform encephalopathies (TSEs) and are harmful pathogens of mammals. These infectious agents of host are made up through aggregation of conformational isomers (PrPSc) and encode glycoprotein (PrPC) of 33-35 kDa. TSEs are the fatal group of diseases which are neurodegenerative and include chronic wasting disease in deer and elk, Creutzfeldt-Jakob disease (CJD) and transmissible mink encephalopathy (TME) in humans and scrapie in goats and

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... sheep. The accumulation of abnormal form of the normal protein (PrP) is common in all diseases related TSE. This abnormal form of PrP called PrPSc is resistant to proteolysis as well as infectious. Present study was conducted in order to do sequence analysis of prion protein gene in twelve breeds of the sheep. We studied this gene to elucidate 12 of Pakistani sheep breeds and to compare gene order with other mammalian species. PCR amplification of 771 bp fragment was done on selected samples from all twelve breeds followed by sequencing. Sequence analysis was done and some sites were found to be heterozygous. These findings on prion protein gene in sheep will provide assistance for further studies on pathogenesis, cross-species transmission, breeding programs, resistance and susceptibility to scrapie.