Prion diseases, termed transmissible spongiform encephalopathies, occur both in humans and ani- mals. According to the hypothesis proposed by Prusiner (1998), the pathogenic agent is prion pro- tein, which forms a molecule with pathogenic properties as a result of conformational changes. The bovine PRNP gene has been localized on chromosome BTA13 at position q17. The struc- ture and organization of this gene have already been identified and described (Horiuchi et al. 1998; Hills et al. 2001). Deletion of 24 nucleotides within the ORF region and transition within the 3’ flanking fragment of the third exon were detected first (Goldmann et al. 1991). The total estimated number of mutations identified to date is about 60 (Sander et al. 2004). Studies conducted so far have been dominated by searching for a relationship between PRNP octa-peptide repeat polymorphism within the third exon ORF and BSE incidence (Goldmann et al. 1991; Leone et al. 2002; Walawski and Czarnik 2003). The studies conducted by Sander et al. (2004) on 7 German cattle breeds demonstrated that the factor enabling to differentiate between clinically healthy and infected animals is dele- tion/insertion polymorphism within the promoter sequence (23 bp) and intron 1 (12 bp). The allele with the 23-bp and 12-bp deletions was more fre- quent in the group of infected animals than among healthy ones. Further investigations revealed a re- lationship between haplotype variants and PRNP gene transcription (Sander et al. 2005). The fre- quency of mutated fragments of the PRNP gene has been determined in a few populations only (Sander et al. 2004; Seabury et al. 2004; Nakamitsu et al. 2005). The aim of the present study was to identify the deletion/insertion polymorphism of the prion pro- tein (PRNP) gene within the promoter sequence (23 bp), intron 1 (12 bp) and 3’ untranslated region (14 bp) in Polish Holstein-Friesian cattle. Samples for the experiment were collected from 234 randomly chosen Polish Hol- stein-Friesian cows in first lactation and 47 unre- lated sires used for artificial insemination (AI) in 2004. J Appl Genet 48(1), 2007, pp. 69–71 Short communication Deletion/insertion polymorphism of the prion protein gene (PRNP) in Polish Holstein-Friesian cattle Urszula Czarnik 1 , Tadeusz Zabolewicz 1 , Janusz Strychalski 1 , Grzegorz Grzybowski 2 , Marcin Bogusz 1 , Krzysztof Walawski 1 1 Department of Animal Genetics, University of Warmia and Mazury, Olsztyn, Poland 2 Institute of Animal Genetics and Breeding, Polish Academy of Sciences, Jastrzêbiec, Poland Abstract. The aim of the present study was to identify the deletion/insertion polymorphism of the bovine prion protein gene (PRNP) within the promoter sequence (23 bp), intron 1 (12 bp) and 3’ untranslated region (14 bp). DNA was isolated from blood of 234 randomly tested Polish Holstein-Friesian cows and from semen of 47 sires used for artificial insemination (AI) in 2004. No statistically significant differences were found in the frequency of genotypes and alleles between cows and breeding bulls in the 3 analysed polymorphic sites within the PRNP gene. Only 3 haplotypes were identified in sires and 4 haplotypes in cows. Keywords: Polish Holstein-Friesian cattle, prion, PRNP, polymorphism, haplotypes. Received: August 23, 2006. Revised: November 6, 2006. Accepted: December 7, 2006. Correspondence: U. Czarnik, Department of Animal Genetics, University of Warmia and Mazury, M. Oczapowskiego 5, 10–957 Olsztyn, Poland; e-mail:czar@uwm.edu.pl