Final answer:
Prnp knockout in mice sometimes causes alteration of normal prion protein to rogue form due to somatic mutation, which leads to the formation of amyloid plaques.
Step-by-step explanation:
Prnp knockout in mice sometimes causes alteration of normal prior protein (PrP) to rogue form due to somatic mutation. This somatic mutation causes a single amino acid change in a prion protein, leading to refolding from PrP to PrPsc. The abnormal PrPsc can induce abnormal folding in normal PrPc, resulting in the formation of amyloid plaques.