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  #1  
Old 06-22-2012
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Help Microbiology question--need your explanation

Capsides of Coksackies virus A are added to naked genomic material of five different viruses to create composite viruses. After 24hrs in culture the total virus per culture in each of the different systems is determined. Naked genomic material added from which of the following viruses will most likely result in the absence of progeny viruses?

A. Adenovirus
B. Calicivirus
C. Flavivirus
D. Picornavirus
E. Reovirus

I can't figure our the point embedded in this question that requires test takers to know, so please help me out of the confusion. Appreciate all of your suggestions!
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Old 06-22-2012
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The answer should be C) Flavivirus.
The question is basically asking you which of the following viruses is enveloped, if it's enveloped than if you give them nucleocapsid from coxsackie then no progeny will be formed as it still needs an enveloped but the rest are naked.
Hope this was useful.
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Old 06-22-2012
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The answer is E. Reovirus

Practically what you need to understand that postive stranded RNA are a copy of mRNA and they can produce their own proteins once inserted to the cell, while negative stranded RNA viruses have to carry with them RNA depandent RNA polymarase which will make from their RNA a mRNA.

Becuase COXACIE virus is +strand it doesnt have in it's capsid RNA dependent RNA polymerase, when you put inside the genome of -RNA virus like Reovirus then that virus practically wont be able to replicate when it inserts to a cell because it's capsid doesnt contain RNA depandent RNA polymrase (as it is coming from the coxasacie virus).

Hope it was understandable.
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Old 06-23-2012
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Why do you consider reovirus to be a -ve stranded RNA virus when it's dsRNA therefore it should have 1 +ve and another -ve strand. Also can an enveloped virus like flavivirus exist w/out an envelope ( unlike the rest of the viruses listed here which are all naked ) ?
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Old 06-23-2012
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Hi, it's true that Reovirus is double stranded but it's RNA doesnt act as mRNA as it stays double stranded inside the cell and it has to have this RNA dependent RNA polymerase to make it infective, thats why i think for the simplicity they say it's -stranded as it has to have this RNA dependent polymerase as all his other friends who are -stranded.

The envelope doesnt really matter, i will explain.
The most important thing of the evenlope or the capsid is the ability to enter inside the cell, the virus doesnt really care what it has outside of it as long it can get his genome inside the cell.
The capsid of the Cox virus is infective so it will be able to infect any cell and insert the Reo virus genome.
This is also known as phenotypic mixing the method they used.
The progeny though will be only of Reovirus with Reo virus capsid.
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Old 06-23-2012
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Quote:
Originally Posted by modesty View Post
The answer is E. Reovirus

Practically what you need to understand that postive stranded RNA are a copy of mRNA and they can produce their own proteins once inserted to the cell, while negative stranded RNA viruses have to carry with them RNA depandent RNA polymarase which will make from their RNA a mRNA.

Becuase COXACIE virus is +strand it doesnt have in it's capsid RNA dependent RNA polymerase, when you put inside the genome of -RNA virus like Reovirus then that virus practically wont be able to replicate when it inserts to a cell because it's capsid doesnt contain RNA depandent RNA polymrase (as it is coming from the coxasacie virus).

Hope it was understandable.
What about adenovirus..

Adenovirus dsDNA virus.. It itself cannot act as mRNA, it has to be transcribed to mRNA for which DNA dependant RNA polymerase is required??
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Old 06-23-2012
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Quote:
Originally Posted by Rookie View Post
What about adenovirus..

Adenovirus dsDNA virus.. It itself cannot act as mRNA, it has to be transcribed to mRNA for which DNA dependant RNA polymerase is required??
Hi Adenovirus as a DNA virus intregrates into the DNA and it's transcription completely depends on the infected cells' polymerases, so it doesnt to bring anything with him.
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Old 06-28-2012
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Yep, the correct answer is E, Reovirus

Thank you all for the discussion and the detailed explanation!
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