Certified Instrument Specialist (CIS) Exam 2025 – The All-in-One Guide to Achieving Certification Success!

Prions are indeed characterized as infectious protein particles that lack nucleic acid. This distinguishes them from other infectious agents such as viruses and bacteria, which contain genetic material (DNA or RNA).

Prions are misfolded proteins that can induce other normal proteins to also misfold and aggregate, leading to disease. They are responsible for several neurodegenerative diseases, such as Creutzfeldt-Jakob disease and mad cow disease. The key feature of prions is their ability to replicate their misfolded state through a mechanism that does not involve nucleic acid, which is why they do not fit the definitions of traditional pathogens like viruses or bacteria.

In contrast, the other options describe entities that do contain nucleic acids or are based on incorrect classifications. For instance, a virus (the first option) contains either DNA or RNA and replicates by hijacking the host's cellular machinery. The second option implies the presence of nucleic acid within an infectious protein, which contradicts the definition of a prion. Finally, bacteria are distinct organisms with cellular structures and genetic material, making them separate from the definition of prions.