However, the PRNP codon 143 SNP (with Arg instead of His) has been revealed to have a relatively weak influence on scrapie progression compared to two other SNPs at codon 146 (Asp or Ser, instead of Asn) and codon 222 (Lys instead of Gln) [9–11,18,42–45]. This evidence concerns the gene PRNP and scrapie.