Prions can happen multiple ways. In familial (i.e. hereditary) CJD, a mutation in the PRNP gene (DNA) creates an abnormal misfolded protein, i.e. prion. In spor

Prions can happen multiple ways. In familial (i.e. hereditary) CJD, a mutation in the PRNP gene (DNA) creates an abnormal misfolded protein, i.e. prion. In sporadic CJD, it's basically bad luck that the protein gets folded wrong. In acquired CJD, exposure to brain tissue with the prion protein causes it. Once there's a prion, it causes more of the protein to misfold, creating more prions and causing the disease.