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Author Topic: Is A Virus A Living Thing ?  (Read 4973 times)

Offline neilep

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Is A Virus A Living Thing ?
« on: 25/07/2007 17:12:13 »
This is probably one for Dr Chris...I believe he might know something about viruses.

Are Viruses living entities in their own right ?


 

another_someone

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Is A Virus A Living Thing ?
« Reply #1 on: 26/07/2007 03:33:40 »
I think this comes into a similar vein as to whether Pluto is really a planet.

The conventional answer is no, viruses are not living because they do not carry within them the full capacity to reproduce (they need to hijack another cell to reproduce).

Carol-A also suggested her own theory was that because viruses lacked ATP - but I am not convinced by that argument.  I am not even really convinced that there is a clear enough line between viruses and other life to exclude viruses from that classification - but then, I recognise that I am fighting against orthodoxy in that.
 

Offline _Stefan_

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Is A Virus A Living Thing ?
« Reply #2 on: 26/07/2007 08:02:23 »
Does cellular DNA/RNA replicate on its own, spontaneously, or does it require the aid of other molecules?

If cellular genetic material requires the aid of other molecules in order to replicate, then it's technically not self-replicating, isn't it? In that case, it's on par with viral genetic material. But you could then argue that cellular genetic material controls and aids in the production of those molecules which allow it to replicate, so it's a complete independent system, while viruses are just protein packages of genes.

 

another_someone

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Is A Virus A Living Thing ?
« Reply #3 on: 26/07/2007 10:44:39 »
Does cellular DNA/RNA replicate on its own, spontaneously, or does it require the aid of other molecules?

If cellular genetic material requires the aid of other molecules in order to replicate, then it's technically not self-replicating, isn't it? In that case, it's on par with viral genetic material. But you could then argue that cellular genetic material controls and aids in the production of those molecules which allow it to replicate, so it's a complete independent system, while viruses are just protein packages of genes.

DNA certainly cannot replicate itself, since it requires various enzymes to help copy it (DNA polymerase - which are used in the PCR procedure to amplify DNA strands in vitro to help with DNA sequencing of minute quantities of DNA).

Since it seems that RNA can perform some enzymatic actions, I am not sure if RNA can self replicate.  Certainly, the current theory seems to be that in the time before DNA life forms became dominant, there were RNA proto-life forms, and these may well have been self replicating strands of RNA.

Retro viruses (such as HIV) cannot self replicate, since the replicate by inserting themselves into the DNA of the host, and so must use the hosts own replication process for replicating themselves. 

Some viruses are actually DNA viruses, which certainly would again require DNA polymerase to duplicate, and this would be supplied by the host cell.

At the other extreme, there are some viruses that are "double-stranded reoviruses contain up to a dozen different RNA molecules which each code for a mRNA. These all associate with proteins to form a single large complex which is replicated using virally-encoded replicase to form new virions" [from wikipedia].  Since these viruses do encode for their own enzymes to self replicate (although they still need the metabolism of the infected cell to provide the raw materials for replication), I suspect these might be the closest to what might be regarded as self replicating viruses.
 

Offline annie123

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Is A Virus A Living Thing ?
« Reply #4 on: 26/05/2011 05:29:46 »
I've nearly finished a book -called Virolution - Frank Ryan-2009- which talks about viruses in some detail, especially with reference to their role in evolution. Se human genome and virus content. This book could answer somme of your questions.
 

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Is A Virus A Living Thing ?
« Reply #4 on: 26/05/2011 05:29:46 »

 

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