Animal Viruses: DNA Virus Synthesis & Replication - Online Tutor, Practice Problems & Exam Prep

Animal viruses, particularly DNA viruses, replicate within host cells by utilizing the host's cellular machinery. Double-stranded DNA (dsDNA) viruses follow the central dogma, where transcription produces messenger RNA (mRNA), which is then translated into viral proteins. Single-stranded DNA (ssDNA) viruses convert their genome into dsDNA before undergoing similar processes. Both types synthesize viral proteins, including DNA polymerases for genome replication, leading to the assembly of new virions. Understanding these mechanisms is crucial for grasping viral pathogenesis and developing antiviral strategies.

Animal Viruses: DNA Virus Synthesis & Replication

This video, we're going to continue to talk about animal viruses and animal virus infections by focusing specifically on DNA virus synthesis and replication. And so most DNA viruses that contain DNA as their genome will replicate inside of the host cell's cytoplasm. And it'll replicate inside of the host cell's cytoplasm using the host cell's components and hijacking the host cell's cellular machinery. However, most DNA viruses will actually encode their own viral DNA polymerase. And the viral DNA polymerase allows the viral DNA genome to replicate even when the host cell is not replicating. Now moving forward in our course, we're going to talk more details about the synthesis and replication of double stranded DNA viruses, and then later, we'll talk about the synthesis and replication of single stranded DNA viruses. And so I'll see you all in our next video.

Replication of Double-Stranded DNA (dsDNA) Viruses

This video, we're going to talk more details about the synthesis and replication, specifically of double stranded DNA viruses, or dsDNA viruses. And so double stranded DNA virus replication and expression actually follows the same steps as the central dogma of biology, as we talked about it in our previous lesson videos. And so that makes double stranded DNA virus synthesis and replication much easier to understand, because we kind of already talked about this in our previous lesson videos. And so recall that the complementary strands of double stranded DNA are referred to as the plus coding strand and the minus template strand. And so we refer to the double stranded DNA molecule as a plus-minus dsDNA, where again the plus strand indicates that there is a coding strand and the minus strand indicates that there is a template strand in this double stranded DNA molecule. And so, of course, this double stranded DNA molecule we know is gonna follow the same steps of the central dogma biology. And so transcription is gonna be able to produce the messenger RNA, and recall that the messenger RNA is the same exact thing as plus ssRNA or plus single-stranded RNA. And it is plus because it is encoding messages. And so, this mRNA or ssRNA or SS RNA that's made via transcription is then gonna be translated to make viral proteins. And so if we take a look at our image down below, what you'll notice is on the far left hand side we're showing you the double stranded DNA virus genome. And so it's a plus-minus double stranded DNA. And so when this double stranded viral genome is in the cell's cytoplasm, the cell's machinery is going to allow for protein synthesis, which is this entire top pathway, and that's going to occur via transcription where the double stranded DNA is used as a template for building plus ssRNA or messenger RNA. And, of course, this plus ssRNA or messenger RNA is going to encode the messages, allowing for translation to occur, and translation will build the viral proteins. Now these viral proteins can also include viral DNA polymerases that will allow for genome replication of the double stranded DNA virus genome. And so genome replication is always going to entail recreating the original viral genome. And so, the viral genome must be recreated and so of course it's going to lead to even more plus-minus double stranded DNA. And so, basically, the result here is that it's replicating the original genome and it's synthesizing viral proteins. And so once these viral proteins have been synthesized and the original genome has been replicated, then it can move on to the 4th stage of an animal virus infection, which is going to be assembly of these components. We’ll get to talk more about the assembly later in our course. But for now, this here concludes our brief lesson on the synthesis and replication of double stranded DNA or dsDNA viruses. We'll be able to get some practice applying these concepts, and then we'll talk about the synthesis and replication of single stranded DNA viruses. So I'll see you all in our next video.

Replication of Single-Stranded DNA (ssDNA) Viruses

This video, we're going to talk more details about the synthesis and replication of single stranded DNA viruses or ssDNA viruses. And so the good thing is that the replication of single stranded DNA viruses is actually quite similar to the synthesis and replication of double stranded DNA viruses. And really there's only just the addition of an extra step. And so ultimately what happens is that single stranded DNA viruses or ssDNA viruses are going to have a single stranded DNA genome, either a plus single stranded DNA of a coding strand or a minus single stranded DNA of a template strand. And so regardless if it's plus or minus, this single stranded DNA is going to be converted to a plus-minus double stranded DNA or dsDNA. And then at that point, once the double stranded DNA molecule has been generated, it is going to be very similar to the synthesis and replication that we saw with double stranded DNA viruses. And so what that means is that this double stranded DNA can be transcribed to form the messenger RNA or the plus ssRNA, which of course can go on to be translated to make viral proteins. And, this double stranded DNA molecule can also be used to replicate the original genome. And so it is going to be used to replicate this single stranded DNA genome. And so if we take a look at our image down below, we can get a better understanding of the synthesis and replication of single stranded DNA viruses. And so notice on the far left over here that we're showing you the original genome of the virus as it enters into the cell is going to be a single stranded or an ssDNA molecule. Now notice here we're indicating that it is a plus ssDNA molecule, but it could also be a minus ssDNA molecule. Now regardless if it is a plus or minus single stranded DNA molecule, it is going to be converted to a double stranded DNA molecule, a plus-minus double stranded DNA molecule. And then once the plus-minus double stranded DNA molecule has been generated, then synthesis and replication is going to be very similar to what we saw with, double stranded, DNA viruses. And so this double stranded DNA can be used as a template for transcription to build the plus ssRNA or the messenger RNA, and of course we know that the messenger RNA can be directly translated to form these viral proteins. And that includes the formation of viral enzymes, which can be used in genome replication, and genome is always going to replicate the original genome as it entered into the cell. And so what you'll see is that it is going to be plus ssDNA that is going to be replicated here. And so once again, here in this image we're showing you plus ssDNA, but it could also be minus ssDNA. And, the of course it's going to regenerate minus ssDNA if that were the case. But ultimately, once these viral proteins have been synthesized and the original viral genome has been replicated, these components can then assemble with each other, which is the next stage of an animal virus infection that we'll get to talk more about later in our course. But for now, this here concludes our brief lesson on the synthesis and replication of single stranded DNA viruses or ssDNA 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.

Which of the following has never been found in a virus?

• A. DNA.
• B. RNA.
• C. Lipids.
• D. Ribosomes.

Which of the following is not a described type of animal virus?

• A. A virus containing double strand DNA.
• B. A virus containing single strand DNA.
• C. A virus containing single strand DNA and single strand RNA.
• D. A virus containing single strand RNA.
• E. A virus containing double strand RNA.

What step is required in the synthesis of ssDNA viruses that is not required in the synthesis of dsDNA viruses?

• A. The viral ssDNA must be converted to dsDNA before it can be transcribed.
• B. The viral ssRNA must be converted to dsRNA before it can be translated.
• C. The viral ssDNA must be replicated before it can be transcribed.
• D. All of the steps required to synthesize ssDNA and dsDNA viruses are the same.

Here’s what students ask on this topic:

How do double-stranded DNA (dsDNA) viruses replicate within host cells?

Double-stranded DNA (dsDNA) viruses replicate within host cells by following the central dogma of biology. The dsDNA genome enters the host cell's cytoplasm and uses the host's cellular machinery for transcription. During transcription, the dsDNA is used as a template to produce messenger RNA (mRNA), which is equivalent to plus single-stranded RNA (ssRNA). This mRNA is then translated into viral proteins, including viral DNA polymerases. These polymerases are crucial for replicating the viral genome, ensuring the production of new dsDNA molecules. Once the viral proteins and replicated genomes are synthesized, they assemble into new virions, ready to infect other cells.

What is the role of viral DNA polymerase in DNA virus replication?

Viral DNA polymerase plays a critical role in the replication of DNA viruses. It is an enzyme encoded by the viral genome that allows the viral DNA to replicate independently of the host cell's replication cycle. This means that even if the host cell is not actively dividing, the viral DNA polymerase can still replicate the viral genome. This enzyme ensures the production of new viral DNA molecules, which are essential for the synthesis of new virions. By hijacking the host's cellular machinery, viral DNA polymerase facilitates the continuous replication and propagation of the virus within the host.

How do single-stranded DNA (ssDNA) viruses replicate their genome?

Single-stranded DNA (ssDNA) viruses replicate their genome by first converting their ssDNA into double-stranded DNA (dsDNA). This conversion can occur regardless of whether the ssDNA is a plus (coding) or minus (template) strand. Once the ssDNA is converted into dsDNA, the replication process mirrors that of dsDNA viruses. The dsDNA serves as a template for transcription, producing messenger RNA (mRNA), which is then translated into viral proteins. These proteins include viral enzymes necessary for genome replication. The dsDNA is also used to replicate the original ssDNA genome, ensuring the production of new viral particles.

What are the key differences between the replication of dsDNA and ssDNA viruses?

The key difference between the replication of double-stranded DNA (dsDNA) and single-stranded DNA (ssDNA) viruses lies in an additional step required for ssDNA viruses. While dsDNA viruses directly use their genome for transcription and replication, ssDNA viruses must first convert their single-stranded genome into double-stranded DNA. Once this conversion occurs, the replication process for both types of viruses becomes similar. The dsDNA is transcribed to produce messenger RNA (mRNA), which is then translated into viral proteins. These proteins include enzymes necessary for genome replication, leading to the production of new viral particles.

Why is understanding DNA virus replication important for developing antiviral strategies?

Understanding DNA virus replication is crucial for developing effective antiviral strategies. By comprehending the mechanisms through which these viruses hijack host cellular machinery, researchers can identify potential targets for antiviral drugs. For instance, inhibiting viral DNA polymerase can prevent the replication of the viral genome, thereby halting the production of new virions. Additionally, understanding the replication process helps in the development of vaccines and therapeutic interventions that can disrupt the viral life cycle. This knowledge is essential for controlling viral infections and reducing the impact of viral diseases on public health.