An infectious protein is a
A virus
B viroid
C bacteriophage
D prion
The correct answer and explanation is:
The correct answer is D) prion.
A prion is an infectious agent composed of protein material. Unlike other pathogens such as viruses, which contain genetic material (DNA or RNA), prions do not have any nucleic acids. They are misfolded proteins that can cause other normally folded proteins to adopt their abnormal shape. This abnormal folding of proteins can lead to a variety of neurodegenerative diseases, particularly in animals and humans.
Prions are responsible for diseases like mad cow disease (bovine spongiform encephalopathy) in cattle and Creutzfeldt-Jakob disease in humans. The mechanism by which prions cause disease involves the conversion of normal cellular proteins into a misfolded form. These misfolded proteins can accumulate in the brain and cause cell damage, leading to the formation of sponge-like holes in brain tissue, which is characteristic of prion diseases.
Prions are unique among infectious agents because they do not follow the typical biological rules of replication. They don’t require a host cell to reproduce, nor do they contain any genetic material. Instead, they propagate by inducing other proteins to misfold. This ability to cause self-replicating protein misfolding is why prions are considered infectious despite lacking traditional genetic material.
The other options are as follows:
- A virus: A virus is a biological entity that contains either DNA or RNA as its genetic material and requires a host cell to reproduce.
- B viroid: A viroid is an infectious agent composed of a short strand of RNA, without a protein coat, that causes diseases in plants.
- C bacteriophage: A bacteriophage is a virus that infects and replicates within bacteria, containing either DNA or RNA.
Prions stand apart because they are solely composed of protein, making them an exceptional and somewhat mysterious class of infectious agents.