This video, we're going to talk more details about the synthesis and replication of double-stranded RNA viruses or dsRNA 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 plus ssRNA. And recall that this plus ssRNA 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 ssRNA is going to require the function of the replicase enzyme, the RNA-dependent RNA polymerase.
And so, because the double-stranded RNA molecule cannot be directly translated, it's somewhat similar to the minus ssRNA. And what this means is that the replicase 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 replicase enzyme, which in this image is shown here as these purple structures, the replicase enzymes must enter during the initial viral infection, and so they must be present initially.
And so, the replicase enzymes that are present initially, they can use the plus-minus double-stranded RNA genome as a template to make plus ssRNA. And once again, the plus ssRNA is the same exact thing as the messenger RNA. And so, the messenger RNA or this plus ssRNA we know can be translated directly to make viral proteins, or the plus ssRNA can be used to replicate the original double-stranded RNA genome, and that is going to require the function of the replicase 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 replicase enzyme to make plus ssRNA. And again, this plus ssRNA 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 replicase enzyme. And also, the plus ssRNA or the messenger RNA here can also be used as a template by the replicase to replicate the original genome, which is the plus-minus double-stranded RNA genome. And so, once again, upon assembly of these proteins, viral proteins and viral genome, the replicase enzyme must once again be packaged into the virus in order for the replicase enzyme to be present during the initial viral infection.
And so this here concludes our brief introduction to the synthesis and replication of double-stranded RNA or dsRNA 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.