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viroid |
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viroid, microscopic infectious agent, much smaller than a virus virus, parasite with a noncellular structure composed mainly of nucleic acid within a protein coat. Viruses usually are too small (100–2,000 Angstrom units) to be seen with the light microscope and thus must be studied by electron microscopes. ..... Click the link for more information. , that infects higher plants such as potatoes, tomatoes, chrysanthemums, and cucumbers, causing stunted or distorted growth and sometimes death. It can be transmitted by pollen, seed, or farm implements. Viroids are single strands of RNA and lack the protein coat of viruses. They do not code for any specific protein but are able to replicate themselves in the nuclei of infected cells. Some scientists believe viroids are parts of normal RNA that have gone awry. Potato spindle tuber viroid was the first to be identified. viroidInfectious particle that is smaller than any of the known viruses. The particle consists of an extremely small circular RNA molecule that lacks the protein coat of a virus. Viroids appear to be transmitted mechanically from one cell to another through cellular debris. They are of much interest because of their subviral nature and their unknown mode of action. Viroids are agents of certain plant diseases; whether they occur in animal cells is uncertain. viroid [′vī‚rȯid] (microbiology) The smallest known agents of infectious disease, characterized by the absence of encapsidated proteins. How to thank TFD for its existence? Tell a friend about us, add a link to this page, add the site to iGoogle, or visit webmaster's page for free fun content. |
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Updated ICTV list of names and abbreviations of viruses, viroids and satellites infecting plants. Finally, there is the possibility that "some viruses evolved from viroids or virusoids, although it is equally possible that these small RNA, rather than being progenitors of viruses, are recent degenerative products of the more complex self-replicating systems" (p. Another USDA scientist found the first viroid ever identified by scientists when studying potato spindle tuber disease, which is transmitted in tubers and seed. |
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