This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Miscellaneous (Infection), Subject name: Medicine
[{'content': 'Mad cow disease is due to? \nSelect and explain. \nA. Protein mis-folding, B. Bacterial, C. Viral, D. Spirochete', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. (a) Protein MisfoldingRef: Harrison 19th ed. / 444e-9* When a prion enters a healthy organism, it induces existing, properly folded proteins to convert into the misfolded prion form. In this way, the prion acts as a template to guide the misfolding of more proteins into prion form.* All known mammalian prion diseases are caused by the prion protein, PrP. The endogenous, properly folded form is denoted PrPc (for Common or Cellular), whereas the disease-linked, misfolded form is denoted as PrPSc (for Scrapie, after one of the diseases first linked to prions and neurodegeneration.)* The precise structure of the prion is not known, though they can be formed by combining PrPc, polyadenylic acid, and lipids in a Protein Misfolding Cyclic Amplification (PMCA) reaction', 'role': 'assistant'}]