Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!ncar!boulder!pell
From: pell@boulder.Colorado.EDU (Anthony Pelletier)
Newsgroups: sci.bio
Subject: Re: viruses, computer & bio
Message-ID: <10325@boulder.Colorado.EDU>
Date: 28 Jul 89 17:35:50 GMT
References: <20800007@m.cs.uiuc.edu> <1666@jarthur.Claremont.EDU>
Sender: news@boulder.Colorado.EDU
Reply-To: pell@boulder.Colorado.EDU (Anthony Pelletier)
Organization: University of Colorado, Boulder
Lines: 43

>In article <20800007@m.cs.uiuc.edu> mckinney@m.cs.uiuc.edu writes:
>>
>>
(regarding computer viruses and there similarity to biological ones)
>>* First, a bio-virus is one of the simplest ways that DNA has
>>  of replicating itself.  That is, if you view organisms as merely
>>  vehicles which DNA uses to replicate itself, then viruses
>>  represent the minimal means of doing so.
>
In article <1666@jarthur.Claremont.EDU> purves@jarthur.UUCP (Bill Purves) writes:
>Sorry, but this isn't true.  Viruses come closer to representing the
>MAXIMAL means.  A virus is not self-reproducing.  It must subvert the
>molecular machinery of a living organism in order to be replicated.
>
>(bill)

I am not sure if you meant to imply this or not, but, while viruses require
the cell for metabolites, many if not most have their own replication
machinary.  They vary all over the board--Vaccinia is so big and stupid
that it does not even need to get into the nucleus of the cell,
Papillomaviruses are only about 8KB and some RNA viruses are even more simple.

But, I  actually wanted to point out something else.  "Organisms" need not be
self-sustaining, if you allow that a parasite can co-opt host machinary to
survive and still be an "organism."  In fact, it all seems a matter of degree
as to what you call "self-sustaining," anyway.  Perhaps only green plants
can make that claim.  So, viruses, as cellular parasites, can be considered
and organism.  If that is acceptable, then why draw the line there?

The simplest way of replicating (using host proteins) is practiced by
transposons.  These could be considered molecular parasites.
My personal favorites of these are the transposable introns; beasts that can
insert themselves in the DNA but are harmless to the cell since they are
spliced out of the message.  In yeast mitochondria, there is an intron that
encodes a single protein that acts as a transposase AND is used
to assist in splicing out the intron.  And, the phage T4 introns are
self-splicing and (in at least two cases) transposable.  So they are
parasites of parasites.  So, as I asked above, why draw the line at
viruses?  Why not include viroids and virusoids and transposons and even
non-transposable introns--since they probably started as transposable ones.
Anyway, so where do others think the line should be on parasites?

-tony