18. Viruses, Viroids, & Prions
Animal Viruses: RNA Virus Synthesis & Replication
18. Viruses, Viroids, & Prions
Animal Viruses: RNA Virus Synthesis & Replication
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concept
Animal Viruses: RNA Virus Synthesis & Replication
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in this video we're going to continue to talk about animal viruses and animal virus infections by focusing specifically on RNA virus synthesis and replication. And so the majority of RNA viruses that have an RNA genome are going to replicate in the cytoplasm of the host cell. And so RNA virus synthesis and replication is actually going to require a very specific enzyme, a viral RNA, a prelim a race that is often referred to as a replicates enzyme. And so this replicates enzyme is an RN, a dependent RNA polyamorous, which means that this is an enzyme that uses RNA as a template to synthesize new RNA molecules. And so really this replicates enzyme uses RNA to build more RNA. And so we'll be able to see how replicates is used by RNA viruses as we move forward in our course to talk about the synthesis and replication of plus single stranded RNA, the synthesis and replication of minus single stranded RNA and then the synthesis and replication of double stranded RNA it. And so I'll see you all in our next video
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concept
Replication of (+) Single Strand RNA (ssRNA) Viruses
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in this video we're going to talk more details about the synthesis and replication of plus single stranded RNA. Or plus Ss. RNA viruses. And so first we need to recall that the plus S. S. RNA or the plus single stranded RNA is really just a normal messenger or M. R. N. A molecule as we've discussed it in so many of our previous lesson videos. And so that means that this messenger RNA can be directly translated by a host cell's ribosomes to form those viral proteins. And so what you can see is down below in our image on the left hand side over here we're showing you A Plus S. S. RNA molecule which recall is the same exact thing as a messenger RNA A. And M. RNA. And so because the Mrna is the viruses genome it's able to be directly translated to form viral proteins. And so these viral proteins that are translated include the enzyme replicates. And so this viral replication enzyme is able to use the PLUS S. S. RNA. The messenger RNA as a template to make multiple copies of a complimentary minus S. S. R. N. A molecule. And so notice here we're showing you that the PLUS S. S. RNA is used to make a complementary strand of minus S. S. R. N. A. And then the replicates enzyme once again can function to use the minus S. S. RNA molecules as a template to replicate the plus Ss RNA genomes. And so what you'll notice here is that the replicates enzyme is able to use the complimentary minus S. S. R. N. A. To build more plus S. S. R. N. A. And again this is what is needed to replicate the original genome to make more copies of that original genome. And so what's important to note is that the replicates enzyme actually does not enter during the initial viral infection. And so notice that the replicates enzyme is nowhere to be found over here on the left hand side. Instead this replicates enzyme is only going to be translated after entry into the cell. And so the replicates enzyme is only going to be translated after the plus S. S. R. N. A. Has entered into the cell. And then this translated replicates enzyme can be used to make minus S. S. RNA. Which can be used by the replication to make more plus S. S. R. N. A. And so once again recall that this replicates is an RNA dependent RNA polymerase. Which means that it can use RNA to build more RNA. And once again it can use the minus S. S. RNA. To build more RNA. And so that is what is needed to replicate these RNA genomes. And so this here concludes our brief lesson on the synthesis and replication of plus single stranded RNA or plus Ss. RNA viruses. And we'll be able to get some practice applying these concepts and then learn about the synthesis and replication of minus single stranded RNA as we move forward in our course. So I'll see you all in our next video.
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concept
Replication of (-) Single Strand RNA Viruses
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in this video we're going to talk more details about the synthesis and replication of minus single stranded RNA viruses or minus S. S. RNA viruses. Now first we need to recall from our previous lesson videos that minus S. S. R. N. A. Unlike Plus S. S. R. N. A. Cannot be directly translated, recall that it's only the Plus Ss RNA or the M. RNA that can be directly translated. And so the minus S. S. RNA once again cannot be directly translated. However it can be used as a template to synthesize A Plus S. S. RNA molecule or an M. RNA molecule and that is going to require the function of the replicates enzyme to use the minus S. S. RNA as a template to build a plus SSR in it. However, since the minus S. S. RNA cannot be translated to make the replicates ends on this means that the replicates enzyme must actually enter into the host cell during the initial viral infection. And so this is very different than what we saw with the plus Ss RNA viruses. Because recall from our last lesson video with Plus Ss RNA viruses, the replicates enzyme does not enter during the initial viral infection. However, with minus S. S. RNA viruses, the replicates enzyme must enter during the initial viral infection. And so if we take a look at our image down below which you'll notice is on the far left hand side we're showing you the minus S. S. R. N. A viral genome. And what you'll notice about the minus S. S. RNA viral genome is that it cannot be directly translated. And so that means that the replicates enzyme must enter, the replicates enzyme must enter during the initial viral infection. And this replicates enzyme that enters during the initial viral infection. That replicates can use the minus S. S. RNA genome as a template to produce a Plus S. S. RNA molecule. Which recall is really just the messenger RNA that can be translated. And so this newly synthesized plus S. S. R. N. A. Can either be translated to make viral proteins or it can be used as a template by the replicates enzyme. To replicate the minus S. S. RNA genome. And so what you'll notice is by taking a look at our image down below is that the replicates enzyme that enters during the initial viral infection can use the minus S. S. RNA template uh to build a complimentary plus S. S. R. N. A. Which once again is really just the same thing as the messenger RNA. Or the MRNA. And the MRNA we know can be translated directly. And so you can see translation can lead to the synthesis of viral proteins including the viral replicates enzyme. And the plus Ss RNA once again can be used as a template by the replicates enzyme to replicate the original genome. The minus S. S. RNA genome. And so here what we have is once again the minus S. S. RNA genome being replicated. And so what's really important to note is that after the synthesis of viral proteins and the replication of the original viral genome these components need to assemble with one another. And what's really important is that when the new viral particles assemble, it's important that the replicates enzyme is packaged with the minus S. S. RNA genome inside of the virus. And this will allow the replicates enzyme to be present during the initial viral infection, which is critical for minus S. S. RNA viruses. And so this year concludes our brief lesson on the synthesis and replication of minus single stranded RNA viruses or minus S. S. RNA viruses. And we'll be able to get some practice applying these concepts as we move forward in our course. So I'll see you all in our next video.
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Problem
ProblemA positive ssRNA virus:
A
Must first be converted to a mRNA before it can be translated.
B
Can be used to translate viral proteins.
C
Is used to synthesize dsRNA before replication.
D
Is not recognized by host ribosomes.
5
concept
Replication of Double-Stranded RNA Viruses
4m
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in this video we're going to talk more details about the synthesis and replication of double stranded RNA viruses or D. S. RNA viruses. Now we don't typically think of RNA as being a double stranded molecule. However in some cases some viruses can have a double stranded RNA genome. And so first we need to recall from our previous lesson videos that the double stranded RNA genome is going to have a plus or coding strand as well as a minus or non coding template strand. And so this plus minus double stranded RNA genome is a double stranded RNA molecule and double stranded RNA molecules cannot be directly translated. However, the double stranded RNA molecule can act as a template to make, okay, Mhm. Plus S. S. R. N. A. And recall that this plus S. R. N. A. Is the same exact thing as the messenger RNA. And the messenger RNA we know can be directly translated. Now using the double stranded RNA. To make Plus S. S. R. N. A. Is going to require the function of the replicates enzyme, the RNA dependent RNA preliminaries. And so because the double stranded RNA molecule cannot be directly translated, it's somewhat similar to the minus S. S. RNA. And so what this means is that the replicates enzyme must enter with the plus minus double stranded RNA genome as part of the initial viral infection. And so if we take a look at our image down below, over here on the left hand side notice we're showing you the double stranded the plus minus double stranded RNA genome. And this plus minus double stranded RNA genome cannot be directly translated. And so what that means is that the replicates enzyme, which in this image is shown here as this purple structure. These purple structures. The replicates enzymes must enter during the initial viral infection and so they must be present initially. And so the replicates enzymes that are present initially. They can use the plus minus double stranded RNA genome as a template to make plus S. S. R. N. A. And once again the plus S. R. N. A. Is the same exact thing as the messenger RNA. And so the messenger RNA. Or this plus S. S. RNA we know can be translated directly to make viral proteins or the plus as as RNA can be used to replicate the original double stranded RNA genome and that is going to require the function of the replicates enzyme. And so if we take a look at our image down below, notice that the double stranded RNA genome here can be used as a template by the replicating enzyme to make plus S. S. R. N. A. And again this plus S. S. R. N. A. Is going to be the same thing as the messenger RNA. And so it can be used directly in the process of translation to synthesize viral proteins including the viral replicates ends on and also the plus S. S. RNA or the messenger RNA here can also be used as a template by the replicates to replicate the original genome, which is the plus minus our double stranded RNA genome. And so once again upon assembly of these proteins, viral proteins and viral genome. The replicates enzyme must once again be packaged into the viral the virus in order for the replicates enzyme to be present during the initial viral infection. And so this year concludes our brief introduction here to the synthesis and replication of double stranded RNA or DNA. RNA viruses, and we'll be able to get some practice applying these concepts as we move forward in our course. So I'll see you all in our next video.
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Problem
ProblemVirus X, a (-) ssRNA virus, cannot replicate its genome without bringing what into the host cell?
A
Replicase enzyme.
B
Duplicase enzyme.
C
RNA polymerase.
D
Protease.
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Problem
Problem(+/-) dsRNA viruses are most similar to which other type of virus?
A
dsDNA viruses.
B
(+) ssRNA viruses.
C
(-) ssRNA viruses.
D
(+) ssDNA viruses.