Prions are best described as which of the following?

• A. A virus
• B. A misfolded protein that is an infectious agent
• C. A bacterium
• D. A carbohydrate

Answer: (B)

Prions are best described as misfolded proteins that act as infectious agents. They are abnormal conformations of a normal host protein, and they propagate not by carrying genetic material, but by templating the misfolding of additional normal proteins. This unique mechanism lets them cause disease without DNA or RNA, which sets them apart from viruses. They’re not bacteria, which are living cells with their own genetic material and metabolic processes, and they’re not carbohydrates, which are sugars and do not function as infectious agents in this way. The proteinaceous misfolded form accumulates in neural tissue, leading to progressive neurodegenerative diseases such as Creutzfeldt–Jakob disease, scrapie, and bovine spongiform encephalopathy.