18. Viruses, Viroids, & Prions
Viroids
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concept
Viroids
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in this video, we're going to begin our lesson on viral roids. And so first we need to recall from some of our previous lesson videos that viral roids like viruses are also a cellular obligate intracellular parasites. However, unlike viruses which are made of proteins, nucleic acids and sometimes lipids with enveloped viruses, viral roids are only made of nucleic acid, not proteins, not lipids, and more specifically, viral roids are only made of a single short strand of RNA, and this single short strand of RNA tends to form a closed ring and so it's a single strain of RNA forming a ring structure. Now these viral roids are only known to infect and cause disease and plant cells and like plant viruses, these viruses need to enter the host plant cell via wound sites well within the plant that can be caused by physical damage, like for example, an insect causing physical damage. Now Vie Roids actually replicate using a host cell's RNA dependent RNA, a preliminary race, which is going to be some kind of enzyme that is similar to replicate of RNA viruses and viral God's actually do not and code for any proteins. Instead, these viral roids are capable of acting similar to small interfering RNA S or S. I. R. N. S. And what that means is that these viral loads are capable of blocking the expression of plant genes and by blocking the expression of plant genes, it can cause disease. And so if we take a look at our image down below, we can get a better understanding of these viral roids and viral infections. And so Vai roids once again are just going to consist of a single strand of RNA that is going to be circular. In this case you can see it creates the structure that you see here and the virus roid is going to be able to enter a plant cell via wounds. And so here what you can see is a healthy plant. But once it is infected with virus hides it can become an unhealthy plant that has a disease caused by a viral I'd. Now what you'll notice is that viruses do not get translated so that is not what happens to them. Instead viral loads are capable of acting similar to S. I. R. N. S where they block host mRNA translation, preventing the gene expression of the plant genes and so this can lead to disease. And so you can see here that the virus could S. I. R. N. A. That is generated from the viral I'd. Is able to block the host Mrna. And by blocking the host I'M RNA, it prevents translation of the host. M. RNA. And so the these uh host proteins will not be expressed and that can lead to plant diseases. Now there are actually many questions about viruses that still exist. And so there is continued research that is ongoing every day to solve these issues and answer those questions about viral roids. And so for now this year concludes our brief lesson on viral ads and how they are a cellular obligate intracellular parasites that are only made of RNA. And so I'll see you all in our next video.
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Problem
ProblemViroids characteristically are composed of:
A
ssRNA.
B
dsRNA.
C
ssDNA.
D
dsDNA.
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Problem
ProblemViroids are:
A
Small fragments of naked dsDNA that infect plant cells.
B
Small fragments of naked dsRNA that infect plant cells.
C
Small fragments of naked ssRNA that infect plant cells.
D
Small fragments of naked ssRNA that infect animal cells.
E
Small fragments of naked ssDNA that infect animal cells.
F
None of the above.