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HIV-1 vs HIV-2 evol

Biology Department mowjmat at COOP.CRN.ORG
Fri Mar 17 13:33:09 EST 1995


To the VIRO-NET

On March 17, Mike Perdue commented in reference to virus evolution...

...I just wanted to make a short comment on the discussion that brought flu
in as an example.  I don't think you can place viruses into a specific
host-parasite relationship that says that the virus will "evolve" in one
direction or the other.......

Evolution is NOT a directed process, especially the evolution of 
viruses.  Viral evolution is dependent random genetic drift.  As Mike 
Perdue suggests, a virus does not benefit by completely killing its 
host--unless it can transfer rapidly from host to host.  This transfer is 
more productive if it is laterally (to a new host) than serially (to the 
same host).  The viral survial paln is quite different than other 
organisms.  The high population of a viral strain lowers the effects of mutation on 
the stability of the viral population.  Since viruses replicate at very 
high numbers within their host, they can incur significant mutations, 
partly due to the streamlined genome; these mutations are random--natural 
selection then acts upon a randomly mutated population of viruses.  The 
natural selection forces are determined, for the most part, by the host.  
Thus as Mike Perdue mentions, there is not a host-virus evolutionary 
direction.  Viral evolution occurs first via random genetic mutation not 
a host-virus relationship.  The latter acts only after mutation has 
altered in the viral strain.
Jeff Huckaby
Molecular Biology
William Jewell College
Liberty, MO 64068
Email mowjmat at coop.crn.org
	




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