Which of the following is TRUE about Prions?
**Core Concept**
Prions are infectious proteins that cause neurodegenerative diseases in animals, including humans. They are unique in that they do not contain nucleic acids (DNA or RNA), making them the only infectious agents without a genetic material.
**Why the Correct Answer is Right**
Prions are composed of a misfolded protein called PrP (Prion Protein), which is normally found in the brain and other tissues. However, when PrP misfolds, it becomes infectious and causes other PrP molecules to also misfold, leading to the formation of amyloid fibrils and eventually neuronal damage and death. This process is known as templated conversion, where the misfolded PrP protein acts as a template for other PrP molecules to adopt the same misfolded structure. The most well-known prion disease in humans is Creutzfeldt-Jakob disease (CJD).
**Why Each Wrong Option is Incorrect**
**Option A:** Prions are caused by a viral infection. Incorrect because prions are not caused by a viral infection, but rather by a misfolded protein.
**Option B:** Prions are transmitted through the air. Incorrect because prions are primarily transmitted through direct contact with infected tissue or contaminated materials, such as surgical instruments or food products.
**Clinical Pearl / High-Yield Fact**
Prion diseases are always fatal, and there is no cure or effective treatment available. The only way to prevent prion diseases is through strict protocols for handling and disposing of infected tissue and contaminated materials.
**Correct Answer:** C. Prions are infectious proteins that cause neurodegenerative diseases in animals, including humans.