(A) Model of the potato spindle ...Figure 13.2 Replication of two different types of viroid in plants. (Top) Repl...Figure 13.3 Vertical and horizontal transmission of viroids in plants via pollen...Figure 13.4 Properties of three classes of satellite RNAs. Schematic of the RN...Figure 13.5 Replication of satellite RNA. Satellite RNA enters the plant cell ...Figure 13.6 Genome and virus particle of hepatitis delta virus. (A) Schematic ...Figure 13.7 Three epidemics of Creutzfeldt–Jakob disease. The graphs show the ...Figure 13.8 The conversion of nonpathogenic, α–helix–rich PrPC protein to the β–...Figure 13.9 Three mechanisms for the development of human transmissible spongifo...Figure 13.10 Bovine spongiform encephalopathy in cattle and variant Creutzfeldt–...Figure 13.11 Chronic wasting disease in North America. Distribution of cases o...