In the case of classical CJD prions from codon 129 heterozygous patients the transmission efficiency in transgenic mice expressing human PrP 129 methionine varies dependent upon PrPSc type and whether prions are propagated on human PrP with methionine or valine at residue 129 (Asante et al., 2002; Korth et al., 2003; Bishop et al., 2010; Kobayashi et al., 2015). This evidence concerns the gene PRNP and Creutzfeldt Jacob disease.