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Viruses Question

Discussion in 'MCAT Study Question Q&A' started by futuredoctor10, Dec 30, 2008.

  1. futuredoctor10

    Classifieds Approved 10+ Year Member

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    This should be a fairly easy question but I want to make sure.

    Viral DNA is injected into the cytoplasm of the host cell for animal viruses as well as bacteriophages.
    [I am guessing for the animal viruses, the host cell cytoplasm then moves the nucleic acid injected to the host cell nucleus]

    Virus DNA integrates into the host cell DNA in the nucleus (if an animal virus) and in the cytoplasm (if a bacteriophage).

    Correct?
     
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  3. G1SG2

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    I think it depends on which cycle you're talking about. In the lysogenic cycle, the viral DNA becomes integrated in the host cell genome. However, in the lytic cycle, the virus immediately uses the host cell machinery to make more copies of itself and then the cell lysis, releasing the progeny.
     
  4. cyclin M

    cyclin M megaman
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    Considering the fact that bacteria do not have nuclei, integration must be in the cytoplasm. As for integration into eukaryotic genomes, viral DNA I believe is coated w/protective proteins and nucleoproteins that allow it to enter the nucleus through the pores. I'm not 100% sure about this last part though.
     
  5. Ibn Rushd

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    Bacteriophage T4, the model for all bacteriophage questions you'll encounter on the MCAT, does "inject" it's genetic material into bacteria. The same, however, cannot be said of all animal viruses. Most animal viruses are actually endocytosed. After entering the cell, these viruses shed their membranous coat and to expose their genetic material, this process culminates in the infection of said cell.

    As for the integration of viral DNA into host DNA, retroviruses, those that use reverse transcriptase to "convert" single-stranded RNA into double-stranded DNA, are primarily responsible in animals, and lysogenic bacteriophages are responsible in bacteria. It's not a matter of cytoplasm or nucleus, it's a matter of where the genome is found in a cell. If it's in the nucleus, then yes, integration will occur there, if it's in the nucleoid region of a bacteria, then intergration will occur there. It's not rocket science.
     
  6. futuredoctor10

    Classifieds Approved 10+ Year Member

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    Thanks everyone for the helpful responses.

    Ibn Rushd, I know it's not rocket science. Sorry if my question seemed trivial or simplistic but I just wanted to make sure as I indicated in the original post.
     

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