This lesson explores two infectious RNA agents that are simpler than viruses: viroids and virusoids. Although both consist of small RNA molecules, they differ in how they replicate and whether they depend on a helper virus.
A viroid is an acellular infectious agent consisting only of a short, circular RNA strand. Viroids have no protein coat and do not encode proteins. They use the machinery of an infected host cell to replicate their RNA.
All flashcards
What is a viroid?
An infectious agent consisting only of short, circular RNA; it lacks a protein coat and uses host-cell machinery to replicate.
How can viroids spread among crops?
They may spread during crop maintenance or harvesting, through vegetative reproduction, and possibly through seeds or insects.
What is a plant virusoid?
A small, non-self-replicating RNA agent that requires a specific helper virus for replication.
What is a prion?
An infectious, misfolded protein that contains no DNA or RNA genome.
What are transmissible spongiform encephalopathies (TSEs)?
Rare, degenerative diseases caused by prions that affect the brain and nervous system.
Quiz questions
How does a disease-associated prion protein promote the accumulation of abnormal protein?Answer: It induces normal prion proteins to adopt the abnormal shape.
Which description correctly identifies a key feature of prions?Answer: They are infectious proteins without a nucleic acid genome.
Which transmission route is not established for TSEs?Answer: Casual contact with an infected person.
How do viroids replicate in an infected host?Answer: They use the host cell's machinery to replicate their RNA.
Which statement describes typical plant virusoids?Answer: They do not encode proteins, and their RNA participates in RNA replication.
Based on Microbiology by Nina Parker, Mark Schneegurt, Anh-Hue Thi Tu, Philip Lister, Brian M. Forster (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.