Viruses, viroids, and prions are all infectious pathogens that cause diseases to plants and animals. Firstly, viruses are microscopic pathogens that cannot reproduce themselves. However, they have DNA or RNA that helps them to direct an infected cell to multiply their numbers. The viruses have proteins that modify their host cells in order to enhance their replication (Lodish et al. 2008). Viruses are also used in gene therapy treatments where genetically modified viruses are used to convey a foreign DNA into the cells. Secondly, viroids are microscopic RNA molecules that do not contain any protein, and they are infectious in their state as naked RNA molecules (Strauss & Strauss, 2008). All the researched viroids affect plants, and none has been shown to infect animals or humans. The viroids are mainly transmitted during the vegetative propagation of plants, as well as, by the use of unhygienic horticultural or agricultural practices. It is also probable that some of the viroids are transmitted by seeds or aphids.
Lastly, prions are small protein infectious agents that have no nucleic acid genome (Das & Zou, 2016). Previous studies have depicted that prions are resistant to ultraviolet radiations that breakdown nucleic acids; though, they are prone to other substances that disrupt proteins. Prions are known to cause various neurodegenerative diseases that affect mammals and humans (Das & Zou, 2016). Viruses and viroids are life forms, but prions cannot be classified to have life. The viruses and viroids have RNA molecules that help them in the process of replication to form other small pathogens with the same elements as the viruses and viroids (Brenner, Miller, & Broughton, 2002). This portrays that these pathogens have life in them as they are able to replicate. On the other hand, prions are just protein cells that lack the ability to replicate. Thus, they do not support the life of their own. The characteristic or prions to have a resistance over ultraviolet radiation is yet another proof that these disease-causing agents have no life.
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References
Brenner, S., Miller, J. & Broughton, W. (2002). Encyclopedia of genetics . San Diego: Academic Press.
Das, A. S., & Zou, W. Q. (2016). Prions: beyond a single protein. Clinical microbiology reviews , 29 (3), 633-658.
Lodish, H., Berk, A., Kaiser, C. A., Krieger, M., Scott, M. P., Bretscher, A., ... & Matsudaira, P. (2008). Molecular cell biology . Macmillan.
Strauss, E. G., & Strauss, J. H. (2008). Viruses and human disease . Elsevier.
