Viroids
Viroids are
RNA molecules that infect plant cells as conventional viruses do, but
are far smaller (one has only 246 nucleotides)
are naked; that is, they are not encased in a capsid.
viroids Infective forms of nucleic acid without a protective coat of protein; unencapsulated single-stranded RNA molecules. Naked RNA, possibly of degenerated virus, that infects plants.
viroid
(vy-roid)
A plant pathogen composed of molecules of naked RNA only several hundred nucleotides long.
virulent ...
viroid. A portion of infectious nucleic acid, without the protein coat of a virus.
virulence. The relative infectiousness of a bacteria or virus, or its ability to overcome the resistance of the host metabolism.
Viroid. A plant pathogen that consists of a naked RNA molecule of approximately 250-350 nucleotides, whose extensive base pairing results in a nearly correct double helix. (See Satellite RNA.) ...
viroid An infectious agent consisting of a single-stranded RNA molecule with no protein coat; produces diseases in plants.
virulence Degree of pathogenicity of an agent; how much damage the agent can cause.
Viruses -- Viroids -- Prions
The dominant classification system is called Linnaean taxonomy, which includes ranks and binomial nomenclature.
Plant Viruses and Viroids
Carnivorous Plants
Unusual Plants
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Satellite RNA (viroids). A small, self-splicing RNA molecule that accompanies several plant viruses, including tobacco ringspot virus. S&E. See U.S. Department of Agriculture. Self-pollination.
Viroid (← links)
Viroids (← links)
Uridine-specific acid nuclease (← links)
Digoxygenin (← links)
Northern blots (← links)
In situ hybridisation (← links)
Rhabdoviridae (← links)
Bdna (← links)
Phosphodiester bond (← links) ...
Viruses and viroids sometimes employ RNA as their hereditary material.
The two that scientists have discovered are called prions and viroids. A prion is (as far as we know) just a protein. Prions are proteins that can invade cells and somehow direct their own duplication, making more of the isolated proteins.
Viroids (meaning "viruslike") are disease-causing organisms that contain only nucleic acid and have no structural proteins.
in terms of metabolic activity, meaning that many scientists do not actually classify these structures as alive, due to their lack of at least one or more of the fundamental functions by which life is defined. They are classified as viruses, viroids, ...
 See also: Virus, Trans, Cells, Protein, RNA
  
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