Prions are misfolded protein molecules, which propagate by transmitting a misfolded protein state. When a prion enters a healthy organism, it induces existing, properly folded proteins to convert into the disease-associated, misfolded prion form. These newly formed prions then go on to convert more proteins into prions propagating the disease. Bovine spongiform encephalopathy or "mad cow disease" is caused by prions. Mad cow disease is an acquired disease from consuming animal products contaminated with prions. Which of the following is true about individuals suffering from Mad Cow Disease?
a. They have a mutation in the prion protein.
b. Their DNA has the incorrect sequence.
c. There is a problem with one of the amino acids.
d. The three-dimensional structure of the protein has been damaged.
e. They have a mutation in the chaperone protein that initially folds the protein.