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Topic: Virusoid


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  VIRUSOID,
Unlike viroids and viruses, virusoids cannot self-replicate inside a cell.
Instead, the cell must also be infected with a certain “helper” virus, which serves as a host for the virusoid and provides RNA that the latter needs in order to reproduce; the virusoid is thus regarded as a type of so-called satellite RNA.
Among plant diseases associated with virusoids are lucerne transient streak, subterranean clover mottle, and velvet tobacco mottle.
www.history.com /encyclopedia.do?articleId=227565   (163 words)

  
 Viroids and Virusoids - Viroids, Virusoids
Viroids and virusoids are also infectious agents, but they differ from viruses in several ways.
Viroids replicate autonomously inside a cell, but virusoids cannot.
Rather, virusoid replication requires that the cell is also infected with a virus that supplies "helper" functions.
medicine.jrank.org /pages/2942/Viroids-Virusoids.html   (233 words)

  
  Virus - Encyclopedia.WorldSearch   (Site not responding. Last check: 2007-08-10)
It has also been suggested that they may represent extremely reduced microbes, appeared separately in the primordial soup that gave rise to the first cells, or that the different sorts of viruses appeared through different mechanisms.
Other infectious particles which are even simpler in structure than viruses include viroids, virusoids, and prions.
Examples of diseases caused by viruses include the common cold, which is caused by any one of a variety of related viruses; smallpox; AIDS, which is caused by HIV; and cold sores, which are caused by herpes simplex.
encyclopedia.worldsearch.com /virus.htm   (2292 words)

  
 Viroids and Virusoids
Viroids, virusoids and prions are unusual infectious agents characterised by having a very small genome and in the case of prions, possibly no genome at all.
Five virusoid RNA genomes are 220-338 nucleotides long, circular, single stranded and possess a ribozyme activity.
Virusoids belong to a larger group of infectious agents called satellite RNAs, found in bacteria, plants, fungi, invertebrates and vertebrates.
www-micro.msb.le.ac.uk /3035/Viroids.html   (1325 words)

  
 subcellular
virusoid, it's a circular loop of RNA that can only reproduce in cells infected by a helper virus, the hepatitis B virus.
The first virusoids were discovered in the early 1980s in Australia, associated with viruses causing diseases such as velvet tobacco mottle (VTMoV), solanum nodiflorum mottle (SNMV), lucerne transient streak (LTSV), and subterranean clover mottle (SCMoV).
An interesting theory about the origin of virusoids is that in plants infected with both viruses and viroids, the viroids got encapsidated in the viruses and later lost their ability to reproduce independently.
math.ucr.edu /home/baez/subcellular.html   (6708 words)

  
 Plant pathogenic RNAs and RNA catalysis -- Symons 25 (14): 2683 -- Nucleic Acids Research
The two viroids and the four viroid-like satellite RNAs or virusoids associated with the four helper Sobemoviruses (Table 1) are isolated from infected plants in the circular form.
A fascinating aspect of 12 viroids, including ASBV and PLMV, and of the human hepatitis delta RNA, a 1700 nt single stranded circular RNA with some viroid-like features (51), is the pattern of purine and pyrimidine tracts which make up substantial portions of their genomes (52).
Relevant to this aspect is the possibility that such tracts may function as organelle localisation signals (53), for the nucleus in the case of PSTV, CEV and CCCV (13 -15) and hepatitis delta RNA (54), and the chloroplast for ASBV (13).
nar.oxfordjournals.org /cgi/content/full/25/14/2683   (5361 words)

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