Viral Replication

[Ronin786]

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Can someone explain this for me?

I came across a Uworld question #374 and it has me going in circles.

They don't offer any sort of explanation, which is very uncharacteristic of them and I can't understand what they mean by template and progeny.

Thanks.

 

[Ronin786]

Well thankfully the Micro cards had a better explanation.

Basically Hepatitis is a partial DS DNA virus that has to be completed into a full DSDNA by its DNA-Dependant DNA polymerase. Then that complete DSDNA is made into a RNA template by the cell's RNA polymerase. Then that RNA template either codes for viral protein or is transformed into a Partial DSDNA by the virus's Reverse Transcriptase.

So in essence, the Hepatitis virus has a Reverse Transcriptase and a DNA-Dependant DNA Polymerase. Which is actually what it says in First Aid, but their wording made absolutely no sense to me.

As for the others, DSDNA replicates its genome by making a DSDNA intermediate, and the same goes for SSDNA except their output is SS.

And for the RNA viruses, +/- makes its opposite template which then turns into its opposite giving the same. Except for Retroviruses which use a DSDNA intermediate.

Please someone correct me if I'm wrong.

 

[Phloston]

Well thankfully the Micro cards had a better explanation.

Basically Hepatitis is a partial DS DNA virus that has to be completed into a full DSDNA by its DNA-Dependant DNA polymerase. Then that complete DSDNA is made into a RNA template by the cell's RNA polymerase. Then that RNA template either codes for viral protein or is transformed into a Partial DSDNA by the virus's Reverse Transcriptase.

So in essence, the Hepatitis virus has a Reverse Transcriptase and a DNA-Dependant DNA Polymerase. Which is actually what it says in First Aid, but their wording made absolutely no sense to me.

As for the others, DSDNA replicates its genome by making a DSDNA intermediate, and the same goes for SSDNA except their output is SS.

And for the RNA viruses, +/- makes its opposite template which then turns into its opposite giving the same. Except for Retroviruses which use a DSDNA intermediate.

Please someone correct me if I'm wrong.

What you've said is correct.

mRNA needs to be made from a DNA template. The template in HepB is a complete DS-DNA intermediate, made from its partial DS-DNA genome via viral DNA-dependent DNA-polymerase. Once that mRNA is made, it is used to make viral proteins via host translational machinery as well as to produce more partial DS-DNA via viral RNA-dependent DNA-polymerase (reverse transcriptase).

For SS(-) RNA viruses, the RNA is not mRNA equivalent, so they use viral RNA polymerase to get to the SS(+) RNA form, which is mRNA equivalent.

 

[Ronin786]

Ironically enough, I just got a question about this on an NBME and ended up getting it wrong.

 

[Phloston]

Ironically enough, I just got a question about this on an NBME and ended up getting it wrong.

That's a gift then. Learn it now versus never.

 

[theTruth_97]

What you've said is correct.

mRNA needs to be made from a DNA template. The template in HepB is a complete DS-DNA intermediate, made from its partial DS-DNA genome via viral DNA-dependent DNA-polymerase. Once that mRNA is made, it is used to make viral proteins via host translational machinery as well as to produce more partial DS-DNA via viral RNA-dependent DNA-polymerase (reverse transcriptase).

For SS(-) RNA viruses, the RNA is not mRNA equivalent, so they use viral RNA polymerase to get to the SS(+) RNA form, which is mRNA equivalent.

does the Hep B viral particle carry an enzyme with dual action- one with both DNA-dependent DNA polymerase activity and reverse transcriptase activity? or does it have two different enzymes with their respective different actions?