Biology · BIOLOGICAL CLASSIFICATION

Neurological disorders such as Bovine Spongiform Encephalopathy (BSE / mad cow disease) in cattle and its human analogue Creutzfeldt-Jakob Disease (CJD) are transmitted by which class of infectious agents?

1. Low-molecular-weight free RNA viroids
2. Helical polyhedral double-stranded DNA viruses
3. Abnormally folded infectious protein particles known as prions
4. Obligate parasitic fungi belonging to Phycomycetes