Are viruses alive?

Keith Robison robison1 at
Sun Jul 19 13:21:05 EST 1992

una at (Una Smith) writes:

>eanv20 at (John Woods) writes:

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

>drw at (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 friend and I recently got into this discussion.  If viruses are
alive, are plasmids?   Transposons?

>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

A good starting place is:

Weissmann, C.  1991.  Nature 352:679-683.
	A 'unified theory' of prion propagation.

I saw a new review of prions recently, but forget where.  Quite likely
it was in "Current Biology" or one of its kindred.

Keith Robison
Harvard University
Program in Biochemistry, Molecular, Cellular, and Developmental Biology

robison at 

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