Genetic RNA:
Introduction:
A list of few RNA Viruses, Viroids and Virusoids:
Virus |
Shape |
Nature |
Size and number of genome |
Single stranded; +/- sense |
TMV (Tobacco mosaic virus) |
Rod |
Naked |
RNA-Single, 6395 ntds |
Single stranded, (+) sense |
RSV (Rous sarcoma Virus) |
Isometric |
Enveloped |
RNA-2n, 8000 ntds |
Single stranded, (+) sense |
Picorna virus |
Isometric |
Naked |
RNA-Single, 7433 ntds |
Single stranded, (+) sense |
Rhabdo virus |
Bullet |
Enveloped |
RNA-Single, 11,000 ntds |
Single stranded, (-) sense |
Influenza virus |
Spherical |
Enveloped |
RNA-Eight, size vary |
All single stranded, (-) sense |
Reo Virus
|
Isometric |
Naked |
RNA-Ten, size vary |
All double stranded, (+/_) sense |
MS2, Qbeta, phages |
Isometric |
Naked |
RNA-4400 ntds, One, |
Single stranded, (+) sense |
HTLV-I and II |
Isometric |
Enveloped |
RNA-Two, ~8.2 Kb each |
Single stranded, (+) sense |
HIV-I and II |
Isometric |
Enveloped |
RNATwo, ~8 to 9 kb |
Single stranded, (+) sense |
Viroids |
PSTV |
|
RNA-circular |
Prions-proteins |
Virusoids |
Tobacco ringspot virusoid |
|
RNA |
|
General Features:
RNAs, those, endowed with all potentialities to replicate, mutate, recombine and perform function, are called genetic RNAs, for they act and behave like any DNAs that act as genetic materials. Almost all genetic RNA are found in few classes of viruses and viroid’s and virusoids.
Viroids: Thy are little larger than Proteinaceous Prions. Viroids contain short RNA without proteins. The size of Viroidal RNA is about 250-450 nucleotides. Viroids, were the first discovered in 1971, as pantheons Theodor Otto Diener, plant pathologist at the U.S Department of Agriculture's Research Center in Beltsville, Maryland. The first viroid discovered was Potato spindle tuber viroid (PSTV), there are 33 species of PSTV. They don’t code for any proteins replicate using host RNA polymerase II, which canalizes rolling circle model for synthesis using viroidal RNA. Some viroidal RNAs act as ribozymes which cleave and self-ligates. Viroids are considered as relics of ancient RNA world.
Theodor Otto Diener, plant pathologist at the U.S Department of Agriculture's Research Center in Beltsville, Maryland, found that most of the viroids replicate in the nucleus or in chloroplasts. Using host RNA PoI catalyzes rolling circle production using viroidal RNA
httrp://www.wikimedia.org; PSTV viroid.
Virusoids: They are single stranded, circular RNAs; they are dependent on plant viruses for their replication and their viral coating. The size of RNA can be several hundred nucleotides long. They replicate by rolling circle mode. Virusoids are often called Satellite nucleic acids, now they are called satellites.
Prions: They are infectious agents composed of proteins only called Prps. They are infectious agents. Their proteins can fold into different forms; some of them cause bovine spongiform encephalopathy (BSE)—called mad-cow disease. Human prion diseases include Creutzfeldt–Jakob disease (vCJD) and its variant Gerstman–Sträussler–Scheinker syndrome, fatal familial insomnia, and kuru. Prions on infection causes human proteins to fold into misfolded prion form. Prions are found in plants as well as animals including humans.
Prion: http://virology-microbiology-b.blogspot.in/
Prions;https://en.wikipedia.org