Revising the meaning of 'prion'

A team of Whitehead Institute and Stanford University scientists are redefining what it means to be a prion—a type of protein that can pass heritable traits from cell to cell by its structure instead of by DNA.

Cellular stress can induce yeast to promote prion formation

It's a chicken and egg question. Where do the infectious protein particles called prions come from? Essentially clumps of misfolded proteins, prions cause neurodegenerative disorders, such as mad cow/Creutzfeld-Jakob disease, ...