Are viruses alive?

Una Smith una at phy.duke.edu
Sat Jul 18 13:08:44 EST 1992


eanv20 at castle.ed.ac.uk (John Woods) writes:

>   P.S. Are viruses alive or dead?  Just a thought.

drw at banach.mit.edu (Dale R. Worley) writes:

>The absolute, eternal dogma (for the last decade or so) is "Life is
>self-replicating information."  Thus, it's the genetic information
>inside you that is the part that is *really* alive.  And viruses are
>alive, although they're dormant most of the time.

Viruses are _not_ self-replicating.  They are (we think) evolved
from self-replicating, living cells.  In the course of evolution
viruses have discarded all but a very few genes, and now depend
on the host cells which harbor them to replicate the viral DNA 
and build the viral coat proteins.

This is at best a very indirect form of self-replication, and I
do not think it is problematic for theories of life, just as I 
don't think parasitic plants which have lost the ability to 
photosynthesize are a problem for general theories or definitions
of plant life (as discussed recently in bionet.molbio.evolution).
Viruses are alive in that they evolved from living organisms...
A more interesting case is the strange class of proteins which
parasitize RNA in sheep, causing the sheep to produce copies of
the (foreign) proteins rather than normal sheep proteins.  Does
anyone have references for this disease?

	Una


-- 

Una Smith   una at phy.duke.edu    School of the Environment
                                Duke University
                                Durham, NC  27706



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