Virus viroids and prions

And viroids are smaller than viruses because they're only made of a single strand of circular RNA. Up until very recently, they were pretty much only found to infect plants, which I hope you can remember because I've written this in green, and I've drawn this funky little bush thing on top of some grass. And today, viroids have been found in humans, in the case of Hepatitis D. So how do viroids make more of themselves if they only are made of circular RNA?

Well, you can think of this in terms of Cs. Because it's thought to be catalytic RNA. So C for catalytic and C for circular. And catalytic RNA means that it can make or break covalent bonds, another C. And because it can do that, it can self-cleave to create more viroids. Now, there's one thing to really pay attention to. You don't wanna confuse viroids with virions. Because virions are what we call whole viruses. That means the protein coat plus the RNA, or maybe an envelope.

Because once a virus gets inside of a host, and the protein coat falls off, it's only genetic material at that point. So that helps distinguish between a virus outside of a cell, and a virus inside of a cell. So remember, viroids and virions are different. And now, let's talk about prions, which are kind of funky. Measurement of the scrapie agent using an incubation time interval assay.

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A comparison of the ultraviolet light sensitivities of PSTV, tobacco ringspot virus, and its satellite. Associated Data Supplementary Materials. Support Center Support Center. External link. Please review our privacy policy. PSTV resisted inactivation by these procedures, which modify proteins. Earlier evidence suggested that the scrapie agent is smaller than PSTV. Its small size seems to preclude the presence of a genome coding for the protein s of a putative capsid.