Animal Viruses: 3. Synthesis & Replication

in this video, we're going to continue to talk about animal viruses and animal virus infections. By focusing specifically on the third step of an animal virus infection, which is a synthesis and replication of the virus. And so after the entry and encoding of a virus into a host animal cell synthesis and replication of that virus can begin. And so really there are two main events that are required for complete replication of a virus. The first main event is going to be the synthesis of viral structural proteins including the capsule of the virus. And it also includes the synthesis of viral enzymes and also viral replication enzymes that are needed for the second main event. That's needed for replication of a virus, which is replication of the viral genome. And the viral genome is going to be some form of nucleic acids, some type of DNA or RNA that we'll get to talk more about as we move forward in our course. Now this replication of the viral genome is going to occur multiple times inside of the host cell, which means that many, many copies of the viral genome are going to be replicated. And so if we take a look at our image down below, we can get a better understanding of animal virus synthesis and replication. And so notice that over here on the left hand side, we're showing you an infecting animal virus that has entered into our host cell here and this uh infecting virus is uncoated here where its protein coat is uncoated and the viral genome here is being released into the cell's cytoplasm And so after entry and uncoated of an animal virus into the host cell. Of course this is when synthesis and replication can begin. And so if the viral genome were to be D. N. A. Then this D. N. A. Would need to be transcribed. Uh and so it was going to create viral M. RNA. And so the viral D. N. A. Is used to build viral M. RNA and the host cells transcription machinery is going to be utilized in order to allow for this transcription once the viral MRNA has been made, then the viral MRNA can be translated by the host cell's ribosomes. And so the translation of this viral MRNA results in the synthesis of viral proteins. And so notice down below, we have a collection of viral proteins that are being synthesized including spike proteins and also proteins that make up part of the capsule of the animal virus. And in addition to the structural proteins of the virus that are being synthesized. Also viral enzymes and replication enzymes are going to be made which is going to allow for the replication of the viral genome or viral genome replication. And so notice initially we start with just one copy of the viral genome. But after viral genome replication it creates many, many copies of the viral genome and so after viral genome replication and synthesis of these viral proteins. Then these viral proteins and the viral genome can assemble to form new virus particles, like what we have down below. And so the assembly of the virus is another step that we'll talk about later in our course. But for now we're focusing on this third step of an animal virus infection, which is the synthesis of viral proteins and the replication of viral genome. And so we'll get to talk a lot more about the synthesis and replication uh, step as we move forward in our course. So I'll see you all in our next video.

in this video, we're going to introduce our map of the lesson on animal virus synthesis and replication. Which is actually down below right here. And so what's really important to note is that animal viruses can actually have many different types of genomes and these different types of genomes allows for variations and viral synthesis and replication. And so as we move forward in our course, we're going to talk about all of the different types of viral genomes and we're going to talk about how those viral genomes allow for variations and viral synthesis and replication. And so really what we're saying here is that the mechanism of viral synthesis and replication actually depends on the type of viral genome. And so notice our map down below is really a map of the animal virus genome types. And so really animal virus genomes can be broken up into three major groups. The first group over here on the far left are going to be the D. N. A viruses which of course are going to be viruses that have a D. N. A genome. Either a plus minus Ds. DNA genome where plus minus and D. S. Are just referring to the fact that it is a double stranded DNA molecule that we'll get to talk more about later in our course. And so the Ds here stands for double stranded. As you can see here we have a double stranded DNA molecule or the DNA virus could have a single stranded DNA genome or a plus S. S. D. N. A. Where the S. S. Here stands for single stranded. And once again we'll be able to talk more about these DNA virus genomes later in our course as we move forward. Now the second major group of uh animal virus genomes are going to be the RNA viruses and RNA viruses of course are going to have an R. N. A genome. And so it could either be a plus S. S. RNA genome or a plus single stranded RNA genome where the S. S. Is single stranded. As you see here, it could also be a minus S. S. R. N. A genome where again the S. S. Stands for single stranded and will differentiate between the plus and the minus. Later in our course as we move forward. Or the RNA virus could have a plus minus D. S. R. N. A. Where again the Ds is double stranded RNA. Which is very strange and unique but it can occur in some viruses. And so once again we'll get to talk more about this later in our course. And then once again last but not least. The third group of uh animal virus genome that we're going to talk about are the reverse transcribing viruses which have the ability to reverse transcribe. And we'll get to talk more about what that means and more details about those genomes as we move forward in our course. But for now this year concludes our brief lesson on our map of the lesson on animal virus synthesis and replication. And so we're going to cover this map by following the left most branches first. So we'll talk about the DNA viruses first, then we'll talk about the RNA viruses and then last but not least, we'll talk about the reverse transcribing viruses, so I'll see you all in our next video.

All of the following are types of animal viruses except which of these answers?

• A. Reverse transcribing viruses.
• B. Phage viruses.
• C. DNA viruses.
• D. RNA viruses.

in this video we're going to talk more about the types of animal virus genomes. And so recall from our last lesson video that the synthesis and replication mechanism of an animal virus actually depends on the type of viral genome that the virus has. And so really there are five main types of viral genomes that viruses can have. And notice that we have those five types numbered down below. And the numbers in the text correspond with the numbers that you see down below in the image. Now what you'll notice is that each of these viral genomes is going to have either a plus and or a minus uh indication. And we need to recall from way back in some of our previous lesson videos that the plus strands are going to be coding strands and coding strands are going to directly encode the message for building a product. Now the minus strands on the other hand are going to be non coding strands or in other words they are template strands and so they do not directly encode the message for building a product. Instead these minus strands are going to be complementary to the plus strands. Now the very first type of viral genome that we have listed here is the plus minus D. S. D. N. A. Now every time we C. D. S moving forward you should note that this represents double stranded and so this is plus minus double stranded DNA. And so the plus minus double stranded D. N. A. Is a double stranded DNA molecule as we have learned about it in our previous lesson videos. And so it is going to have one plus strand or one coding strand and one minus strand or one non coding or template strand. And so this double stranded DNA molecule, if it is a viral genome it is going to be expressed by following the normal central dogma of biology which means that the double stranded DNA molecule of the virus is going to be transcribed into an M. R. N. A. And then that M. RNA will be translated into protein. And so if we take a look at our image down below, notice on the left hand side over here we're focusing in on the plus minus double stranded DNA molecule. And so notice that the original molecule at the top here is a double stranded DNA molecule has a plus strand and a minus strand. And so uh this viral genome, if it is a plus minus Ds DNA molecule, double stranded DNA molecule then it is going to be expressed via the normal central dogma of biology which means that it will be transcribed to form a messenger RNA. And we'll learn that messenger RNA is actually synonymous with plus S. S. RNA. Where the S. S. Is standing for single stranded RNA. Or just single stranded. And so we have plus Ss RNA synthesis which is really just transcription. And that's the formation of the plus S. S. RNA. The messenger RNA. And then this messenger RNA of course will be translated using the host ribosomes machinery to form the synthesis of viral proteins. Now we'll get to talk a lot more about this process as we move forward in our course. But right now this is the introduction to plus minus double stranded DNA. Being a possibility for viral genome. Now the second type of viral genome that we have listed is going to be S. S. D. N. A. And S. Is going to stand for single stranded as we move forward through a course. And so this S. S. D. N. A. Is going to be single stranded DNA. And it could either be a plus single stranded DNA. Or coding single stranded DNA. Or it could be a minus single stranded DNA. And we'll get to talk more details about the mechanism of how the single stranded DNA is expressed as we move forward in our course. But really this S. S. DNA. Which can be either plus or minus is gonna be a single stranded DNA molecule and we're going to learn that it is going to need to be converted into plus minus D. S. D. N. A. Before it can actually be replicated and synthesized and the viral proteins can be synthesized. And so notice that the second one that we have right here is going to represent our plus or minus single stranded DNA. And so notice that we only have one single strand of DNA. And what we're going to learn is that before it can be replicated and synthesized, the single strand of DNA will need to become double stranded DNA. Now we're not showing you the double stranded DNA here in this image. But later in our course when we talk more about it we'll show you that process in more detail. But ultimately the single strand of DNA is going to be uh it's gonna be used to build a plus S. S. R. N. A. And so the plus S. S. R. N. A. Is messenger RNA. And then that messenger RNA is going to be translated using the host ribosomes machinery to build viral proteins. And so there are some variations in the synthesis and replication depending on the genome. And once again we'll get to talk more about those variations as we move forward in our course. Now the third type of viral genome is going to be a plus S. S. R. N. A molecule and this is going to be a single stranded RNA molecule that consists of a coding strand. And so really the plus S. S. R. N. A. What's really important for you to note is that the pluses are an A plus S. S. R. N. A. Is the same exact thing as a coding M. RNA a molecule. And so really the messenger RNA is synonymous with PLUS Ss RNA. And so that's really important to keep in mind as we move forward. And so we know already from our previous lesson videos that messenger RNA can be directly translated by host rival zones. And so notice down below if the viral genome is a plus S. S. RNA molecule really it is just an MRNA molecule. And that means that these MRNA molecule can be translated directly by the host ribosome to form viral proteins. Now the fourth type of genome that we have listed here is going to be the minus S. S. RNA which once again the Ss is single stranded RNA. But this single strand is actually a non coding or template RNA molecules. And so this is a non coding single stranded RNA. And because it is non coding it will not be able to be directly translated by the host ribs. Um It first needs to be used to build plus S. R. N. A. And then the plus S. RNA can be directly translated. And so if we take a look at the fourth genome type right here, what we have is minus S. S. R. N. A. And this minus S. S. RNA. Once again it can be used to build plus Ss RNA, the messenger RNA. And it's the plus S. S. RNA. Or the messenger RNA. That can be directly translated by the host rob zone to form viral proteins. And once again we'll be able to talk more details about each of these different types of genomes as we move forward in our course. Now the fifth and final type of viral genome is going to be the plus minus Ds RNA, which is really just the plus minus double stranded RNA which is very strange and really unique to these special types of viruses that have them. And so this is going to be a double stranded RNA molecule that has both A plus R. N. A. Or coding RNA strand and a minus RNA or a non coding or template RNA strand. And so this double stranded RNA molecule is going to be a template to make plus S. S. RNA. Or messenger RNA. And once that plus Ss RNA has been made it can then be translated. And so notice down below in our fifth and final genome type, we have the plus minus D. S. R. N. A molecules, double stranded RNA. And so notice that we have a double stranded RNA molecule and it is going to be needed uh to you it's going to be used to build a plus S. S. R. N. A molecule, a messenger RNA. And that messenger RNA can again be directly translated by the host cells ride his own forming viral proteins. And so there are uh there is a lot of information here in this video but we're going to break it down even more as we move forward in our course. So really this is just the introduction to these five different types of viral genomes and once again we'll get to talk a lot more about them as we move forward in our course. Now, one thing that you should know that is going to be similar across all these different types of viral genomes is that in the process of synthesizing new viral proteins, all of them must eventually generate plus S. S. R. N. A. At some point. And that plus Ss RNA is really just messenger RNA. And that messenger RNA is what can be directly translated to form viral proteins. And so that is a common feature across all these different types of viral genomes and the synthesis of those proteins. And so once again we'll get to talk a lot more about these different types of animal virus genomes and the variations and the synthesis and replication mechanisms between them as we move forward in our course. So I'll see you all in our next video.

in this video we're going to talk about some common themes of all virus genomes. And so regardless of the viral genome type, all viruses must complete two tasks. The first task as they must all recreate their original genome type regardless of what that original genome type was. For example a double stranded RNA virus is going to contain a double stranded RNA genome as its original genome. And so this double stranded RNA virus must recreate the double stranded RNA genome in order for it to replicate properly. Now the second main task that every virus must accomplish is that every virus must make Plus S. S. RNA and recall that Plus S. S. R. N. A. Is the same exact thing as MRNA or messenger RNA as we've talked about it before in our previous lesson videos. And so all of these different viruses must make this PLUS Ss RNA or messenger RNA because the messenger RNA is what can be directly translated into protein. And so all of these viruses, regardless of the viral genome type, must eventually make PLUS S. S. RNA or MRNA. And that is in order for the host cell's ribosomes to synthesize viral proteins. And so what you'll notice up above in this image once again is that regardless of the type of viral genome, all viral genomes must accomplish the task of making PLUS S. S. RNA at some point they must all make plus Ss RNA or messenger RNA at some point in order to synthesize proteins. And so notice that that is a common theme across all of these different types of viral genomes, regardless of the type that they are. And so that's something important to keep in mind. And once again in addition to making Plus S. R. N. A. As a common theme, all of them eventually must recreate their original genome. And we'll talk about the mechanisms of how each of these different types of animal virus genomes is able to replicate as well as synthesized viral proteins as we move forward in our course. But for now this year concludes our common themes of all virus genomes, how they must all recreate their original genome type and how they must all eventually make plus us as RNA or messenger RNA. And so I'll see you all in our next video.