Final answer:
d. they lack nucleic acid
Prions are different from other infectious agents because they lack nucleic acids, and instead of containing DNA or RNA, they replicate by converting normally folded proteins to abnormally folded forms that accumulate and cause disease.
Step-by-step explanation:
Prions are distinct from other infectious agents because they lack nucleic acid. Unlike bacteria, viruses, and other pathogens that contain DNA or RNA to replicate, prions are infectious proteins that do not carry genetic material in the form of nucleic acids. Instead, prions replicate by inducing normally folded proteins (PrPC) to convert into the abnormal prion form (PrPSC), which is folded abnormally. This misfolded state propagates by altering the conformation of neighboring normal proteins to the misfolded prion form, leading to a chain reaction. The accumulation of these misfolded proteins in tissues, especially the brain, is associated with cellular damage and a number of neurodegenerative diseases, such as mad cow disease and Creutzfeldt-Jakob disease.