Talk:Viroid
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[edit] Taxonomy
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I find that there are references to domain virus, and aphanobionta to categorize these things (the domains covering the same content) ; and there's the superkingdom Acytota 132.205.15.43 20:20, 25 Nov 2004 (UTC)
[edit] WikiProject
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[edit] detecting viroids
I reluctantly reverted the addition of To determine whether an infectious agent is a viroid, culture the substance by itself on a nutritive medium, away from plant cells.
While this would certainly distinguish viroids (which wouldn't grow) from bacteria (which would grow on the media), this does nothing to distinguish between (RNA) viroids and DNA viruses -- right?
So how does one determine whether an infectious agent is a viroid? Or, in practice, do we not bother -- we just use the "culture" test to decide whether to use an antibacterial treatment, or instead the other treatment that generically applies to virus, viroid, virusoid, etc. ?
The virus page mentions RNA viruses and DNA viruses. What is the difference between a "viroid" and a "RNA virus"? Or are they the same thing?
--DavidCary 14:08, 13 December 2005 (UTC)
- The edit you reverted was really a nonsense. However, there is a big difference between viruses and viroids - viroids do not code their own proteins but are autocatalytic RNAs. RNA viruses code proteins. There are also virusoids, which do not code proteins, but are dependent (paraziting) on a virus. There is no general antivirus treatment (nor antiviroid etc.), there is even no general antibacterial treatment. --Kyknos 19:33, 13 December 2005 (UTC)
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- I'd even be cautious to suggest a close evolutionary relationship between viri and viroids. Viroids really seem to be "escaped introns" or more specifically, autocatalytic transgenes. While a virus during its lysogenic phase has something like a rudimentary sort of "life" (i.e., it causes proteins to be produced which otherwise wouldn't, and thus does have a non-autonomous metabolism - note that the infectious virus particle itself is definitely non-living), viroids seem to be "genome detritus" so to speak.
- How to detect them? Tough, very tough. At first, somebody has to suspect that there is something odd going on, which is quite tough as these things are often enough symptomless. Then, you need to do RT-PCR, reversely transcribing the RNA prsent in a cell into DNA. Then, you have to note that there is a large quantity of RNA present in the original sample which does not come from the host (i.e. does not map onto the host genome in DNA sequence). And having thus determined the viroid sequence (hopefully), one could use molecular probes to fish for denaturated viroid DNA (heated, so that it does not align in double strands). IONO whether it is done that way, but it would work.
- It might be added (ref?) that the mode how viroids cause pathogenic effects is unknown, but possibly has something to do with them interfering in host DNA directly (i.e., physically), compare Antisense DNA (which is single-strand however) - viroids might do it by "edging" their way into the DNA transcription/replication apparatus. Molecular monkeywrenching might be a quite appropriate expression - IF that hypothesis is correct. Dysmorodrepanis 18:26, 22 October 2006 (UTC)
