Viral Genetics

by Jason Amores Sumpter
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Hello, everyone. In this lesson, we're going to be talking about the different groups and classifications of viruses, depending on the amount and type of genetic material that they have. So viruses, even though they are not alive, are going to have genetic material that contains the blueprints for new viruses. And they can either have a DNA virus or RNA virus, meaning that they can have a DNA genome or a Arna genome. Now these different genomes can come in the form of double stranded DNA or RNA, or single stranded DNA or RNA. So first, let's talk about double stranded DNA viruses and double stranded RNA viruses. Double stranded RNA viruses are going to have a genome that's very similar to ours. They're going to have double stranded DNA to make up their genetic material. And because it's so similar to our genome, whenever the virus enters into the cell, it can easily be replicated because it often replicates with the genome. During s phase, Double stranded DNA viruses often integrate themselves into our genome so that any time we replicate our genome, the viral genome is replicated as well. Now they're going to infect a wide array of organisms, including US, including bacteria, including all sorts of organisms except land plants, which I always thought was interesting. Land plants don't have double stranded DNA viruses. Now there's also double stranded are in a virus is double stranded. RNA viruses are not as common as single stranded RNA viruses, but they're still very important. Double stranded RNA viruses are going to be a little bit different. They are going to enter. The site is all, and because they are double stranded, are in a viruses they conserve as a template for synthesis. They can actually serve as a template to create the viral proteins that are needed because it's already RNA, and it's already going to have our name molecules that can be translated. So this allows the viral enzymes to be made. And then these viral enzymes are made, and then the viral genome can be replicated as well. And this is going to include ah whole bunch of organisms that can be infected, including fungi, plants, vertebrates, bacteria and insects. So a ton of different organisms are infected by double stranded Arning viruses. Now we're going to talk about single stranded RNA viruses, which you're going to be the most common type of virus that you will ever hear off. Now if you guys wanted some examples off double or if you wanted some examples of DNA viruses, smallpox is a DNA virus. Herpes is a DNA virus, and chicken pox, I also believe, is a DNA virus. Most viruses where familiar with they're going to be RNA viruses, and most of those were going to be single stranded RNA viruses. Now I'm going to go over this topic first before we talk about single stranded RNA viruses because single stranded RNA viruses can come in two forms. But I want to go over a concept before we talk about those two forms. So what do we have here? Do you guys know? Well, this is the process of transcription whenever we which we already learned about whenever we learned about DNA expression. So this is the process of transcription, and this Marna in blue is being made by the RNA prelim race, actually reading the genetic code, the DNA and building an m. R n a strand off of this genetic code. So this is the DNA, and then we have our RNA pull. Emory's Now, Whenever we talked about creating Marna, we talked about the coding DNA Strand and the template DNA strand. Now there are many names for the coding strand, and there are many names for the template strand. You guys might also remember that the coding strand can also be called the Sense Strand, and it's also called the Positive Strand. For whatever reason, the coding strand has three different names. Remember the coding Strand is going to have the same exact code as the Marna. So the coding strand equals the code of the Marna. They have the same exact code. Now. We also have the template strand here, which is very important. The template Strand also has its own unique names. It's either called the Template strand. It's either called the anti sense strand or it's called the Minus Strand. Now I know that it sucks that we have to remember all these different names of these DNA strands, but they are going to become very useful. Let me rewrite that since you guys can't really see it. So the minus strand. Okay, so the template strand is called the anti Sundstrand anti minus strand and the template strand is going to be complimentary. Thio. The M r N A. So the template strand is complimentary to the Marna. And that is because the template strand is utilized to build the Marna. So they're going to be complementary to each other while the coding strand in the Marna are going to be exactly the same code. Now, remember that the coding strand is also called the plus strand, and the template strand is also called the minus strand. So now we know what plus and minus actually means. Plus strands have the same code as the Marna minus strands have the complementary code to the Marna. That's going to become very important because, as you guys will see, there are two different types off single stranded RNA viruses. You can have a positive sense strand RNA viruses, and you can have negative or minus since strand RNA viruses. And this is going to tell you whether the single stranded RNA genetic code off this particular virus is equal to the Marna or complementary to the M R N A. That is made for this virus. So we have these two different types. We're going to have the positive sense strand and the negative sense strand for the RNA virus. So the positive sense are in a virus is a single stranded RNA virus. So just you guys know these air all single stranded Arnie. It's gonna be a single stranded RNA virus genome that contains the same sequence needed to produce the viral proteins. So that means that this particular genome is the coding strand. So the genome equals the coding strand or the positive strand. Okay, So because it is the coding strand, that means that the genomes code is exactly the same as any more n A. That would be made from that genome. So what does that tell us? Well, that tells us that the genome could enter the cell the host cell and immediately transcribed into translate. Excuse me? That is a type of immediately translate into proteins because the coding strand is the exact same code as the Marna. Well, the virus could simply send its genetic material in and translate that genetic material into viral proteins, which will then begin to build and replicate that virus. So the positive sense are any viruses are very simple. They are the coding strand, which is equal to the Mariana Strand. And when that goes into the host cell because it is equal to the mRNA Strand, it could be directly translated into viral proteins, and that virus will be immediately replicated now. Negative sense are any virus is not so easy. Negative sense aren't a Viruses have a genome that contains the complementary sequence to those that code for the viral proteins. So what does that mean? That means that the genome is the template strand. So what does that mean? Well, that means it's the minus strand, meaning that we have to make an M R N A from this template genome strand to begin creating viral proteins. So we have to make the marina. Where, in the positive sense RNA virus. We didn't have to make the marina because the Marna was equal to the genetic code. So the negative sense strand RNA viruses have an extra step. They have to make an mRNA so viral RNA polymerase must always accompany these viruses into the cell so that the viral RNA preliminaries once this viral genome enters the cell, can transcribe it into the viral M RNA. So viral viral RNA Flynn race must accompany genome to transcribe the RNA into the viral marina so that those viral proteins can be generated. So those were the two different types of single stranded RNA viruses. Now there's another very important type of virus that I would like to talk about. Those air gonna be retroviruses, retroviruses. I'm sure you guys have heard of before. Retroviruses are incredibly interesting because they're able to change their genetic code and have intermediate genetic code. Retroviruses have a very important protein called viral reverse transcriptase, and what's going to happen is thes retroviruses are going to be positive. Single stranded are in a viruses, and they're going to use their viral reverse transcriptase to create complementary DNA from that single strand RNA genome. And then that single stranded DNA complementary DNA is created into double stranded DNA and then inserted into the host genome. Do you guys have any examples, or do you guys know of any examples of retroviruses Really, really good example of a retrovirus? Is HIV HIV does this and it is going to be an RNA virus that is going to use the reverse transcriptase to create a DNA version of its viral genome And then that DNA version will be inserted into the host genome. Okay, everyone All right. So now I wanted to go over one more thing before we end. And that is three different classifications off viruses. You can actually put viruses into groups groups one through seven. So group number one is going to be double stranded DNA viruses, group number to a single stranded DNA viruses, three double stranded RNA viruses, four single stranded plus RNA viruses or plus single stranded RNA viruses. And then you're going have the negative single stranded RNA viruses and group number five and then the last two groups are interesting. So the number six Group six is going to be the single stranded on RNA virus that is going to have reverse transcriptase. So this one here is a retro virus. So these air retroviruses in Group number six group never seven. I didn't particularly talk about because it's very uncommon group of viruses, but these were going to be called Pera Retro viruses. Pere retro viruses are going to be viruses that have double stranded DNA, but they're going to replicate via a single stranded RNA intermediate. They're not very common whatsoever they're not generally talked about. I doubt you guys will be tested upon thes because they are so uncommon. But that is group number seven. Now, if you guys were wondering what some examples of single stranded viruses were for positive, since Strand single stranded are in a viruses three West Nile virus. So this group right here, Group number four, you're going to have the West Nile virus. The common cold is also in group number four, and hepatitis C is also in group number four. But there are a lot of RNA viruses, like a ton of RNA viruses. Rabies, I believe, is also an RNA virus. Ebola, I believe, is also an RNA virus. Influenza and polio are also RNA viruses, so most of the ones we combat on a regular basis we're going to be RNA viruses. But I just wanted you guys to know the difference between our RNA and DNA viruses, single and double stranded viruses. And I wanted you all to know the different groups of viruses that you may need to understand, or you may encounter on a quiz or test. Okay, everyone, let's go on to our next topic