Wize University Biology Textbook > Viruses
Prions & Viroids [Content coming soon]
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Prions
These interesting and deadly proteins are strikingly different from other viruses.
Structure
- Prions are misfolded proteins Example: Prion protein (PrP) is the most common misfolded protein
- The cause of the initial folding error is unknown
- These proteins can be transmitted, affecting other normal proteins
- This is different from all other forms of pathogens known
Prion Diseases
- Many neurodegenerative diseases in vertebrates
- Transmissible spongiform encephalopathies (TSEs)
- Improperly folded proteins create tiny holes in tissue, creating a "spongy" surface Examples: Mad-cow disease and Creutfeldt-Jakob disease in humans
Viriods
These are a unique group that contain the smallest infectious pathogens known! These really push the boundaries of what counts as "living"
Structure
- Just a short strand of RNA
- Circular
- Single-Stranded RNA
- No protein coating
- Do not code for any proteins
- Use host cells RNA polymerase II
- Continuously replicates the viriod
- May be a living relic from the "RNA world"
- May represent a critical step in the creation of life from just RNA
Diseases
- Potato spindle tuber disease
- Range of virulence and symptoms
- Cause leaves to elongate and become "spindle like"
- Slows the rate of sprouting
- Eventually kills the leaf
- Spread by contact or insect vectors
Mark Yourself Question
- Grab a piece of paper and try this problem yourself.
- When you're done, check the "I have answered this question" box below.
- View the solution and report whether you got it right or wrong.
Describe how viroids may represent an initial first step in the formation of life.
Which question best describes a prion disease?