Prions and ViroidsThe tiny, not-so-cute guys that

you don’t see coming!

Prions: Top Five Facts

5How they were

discovered: First observed in

degenerative disease Kuru. Discovered and coined by Prusiner 1982.

4Far to go:

Not much is actually know about prions. Questions such as how do they “replicate” are still unanswered.

Number 3Examples of diseases

caused by prions: Prions cause

neurodegenerative diseases such as: kuru, Creutzfeldt-Jakob, scrapie, and “Mad Cows Disease.”

Number 2Their structure:

A prion is a protein found mainly in the brain. It is not the protein itself that causes disease but only the abnormally folded version of the prion protein also know as an infectious prion.

Number 1How they work:

The infectious prion is somehow capable of inducing of prion proteins to adopt an abnormal configuration. These abnormal proteins cannot be destroyed by lysosomes and they accumulate to cause cell and spongy degeneration of the brain.

Viroids: Top Five Facts

5Discovery:

Considered a major biological breakthrough when discovered by pathologist, Diener, 1971.

4Classification:

Viroids have been classified into two families, three sub-families, and eight genus and species groups. There are still many unclassified viroids.

Number 3Diseases caused by

viroids: Viroids are primarily

associated with plants. Viroids are responsible for crop diseases such as potato spindle tuber, avocado sunblotch, etc. Recently however, it is found that a certain type of viroid plays a role in human hepatitis D.

Number 2Structure:

Viroids are 80 times smaller than normal viruses; formed without a protein coat. Contains short circular RNA strands, but does not encode for any protein products in their structures.

Number 1How they work:

When a viroid enters the host cell it takes over RNA polymerase and produces copies of itself. In this manner it can quickly spread and grows to numerous numbers within a cell before breaking out and spreading to other cells.

Bibliography Pictures In order: http://www.nickcampos.com http://student.biology.arizona.edu http://pubs.acs.org http://plantdiseasehandbook.tamu.edu http://schaechter.asmblog.org http://thevirologyblog.blogspot.ca

Text Reference http://www.atsu.edu/faculty/chamberlain/Website/Lects/PRIONS.HTM http://www.els.net/WileyCDA/ElsArticle/refId-a0000434.html

Audesirk T., Audeesirk G., Byers B. 2008, Pearson Prentice Hall, Pearson Education, Inc, Upper Saddle River, NJ Biology Life on Earth with Physiology pp381-385.

http://mcmanuslab.ucsf.edu http://www.cdc.gov http://www.news-medical.net