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DNA/RNA virus mutation rates

Brian Foley btf at t10.lanl.gov
Wed Sep 3 14:53:21 EST 1997

Michael Goodin wrote:
> why do related viruses eg.
> HIV-1 and HTLV-1 have such different mutation rates if 
> polymerase error is
> the only operating mechanism driving evolution of these viruses.  

	I would not assume that polymerase error is the
only mechanism.  But even if it were, the "rate" of evolution
might better be described in terms of mutations per replication
cycle than mutations per year.  Retroviruses have little chance
of mutating while incorporated into host DNA in the proviral form.
They mutate when they replicate through the RNA form and back
to DNA via reverse transcriptase.  It is also known that the
reverse transcriptase is more error-prone when the pools of 
nucleotides are not optimal.  Thus replication in different cell
types can result in different mutation rates for the same virus.
	Overall, the mutations are only a part of the evolution
of a species.  Selection plays a role that may be equal or greater.
The observed mutations are only a small subset of all mutations,
those that have survived the selection process.  

|Brian T. Foley               btf at t10.lanl.gov                       |
|HIV Database                 (505) 665-1970                         |
|Los Alamos National Lab      http://hiv-web.lanl.gov/index.html     |
|Los Alamos, NM 87544  U.S.A. http://www.t10.lanl.gov/~btf/home.html |

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