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I'm not a professional in biology nor a student, but I'm curious about this. To be more specific: why doesn't a plant virus affect animal cells?

I suspect that different kinds of cells have different ways to replicate DNA and that this is the reason for the specialization of viruses.

I'm wonder if someone in the field can explain it to me. Thanks.

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2 Answers

up vote 9 down vote accepted

Firstly, it's important to recognize that "plant viruses" do not exist. There are only "viruses that affect particular plant cells", or "viruses that affect a particular cell type". You'll see why in a moment.

One of the structural components of many virus is its protein coat. Different types of biological molecules protrude from the surface of this protein coat, deemed signalling molecules. The structure of these molecules are specific to a certain type of virus.

Analogously, specific cell types have specific biological molecules that protrude from their plasma membrane, deemed receptor molecules. For a virus to affect a particular type of cell, their signalling and receptor molecules must "fit within each other", like lock and key. Once they do so, a virus may interact with this molecule, in whichever way it does.

Although your hypothesis wasn't entirely correct, as viral contact with a cell must first be established, viruses do interact with DNA replication in different ways, as in the lytic or lysogenic cycle.

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Let me know if I understand. The specialization of the viruses relies in the initial contact with some specific cell. –  leo Jan 6 '12 at 6:24
    
@leo: in great part. The virus first needs to enter the cell and to do that it needs to recognize some specific protein on the outside of the cell. Then, of course, once inside the cell it needs a specific set of enzymes/protein/conditions that will allow it to replicate. –  nico Jan 6 '12 at 8:56
    
@nico, thanks :-) –  leo Jan 6 '12 at 16:36
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Further to LanceLafontaine's answer I'd just like to mention that, although as he mentioned viruses interact with DNA replication in different ways, DNA replication in itself is the same process in both plant and animal cells. For example, a human cheek cell and a potato root cell replicate their DNA in the same way (as both are eukaryotic cells - cells with internal membrane bound organelle): see Eukaryotic DNA replication for more information.

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Thanks for your answer and your edit. The thing with the plant virus that attack an animal cell was just an example. Originally, I was thinking: why a virus that attack a bacteria do not attack an animal cell. Anyway, the answers here really enlighten me. –  leo Jan 8 '12 at 6:50
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