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From: eddy@boulder.Colorado.EDU (Sean Eddy)
Newsgroups: sci.bio,sci.astro,sci.philosophy.tech
Subject: Re: DNA for interstellar messages
Keywords: realities of viruses and VIROIDS
Message-ID: <2323@boulder.Colorado.EDU>
Date: 28 Jul 88 01:23:37 GMT
References: <6211@bloom-beacon.MIT.EDU> <2863@bath63.ux63.bath.ac.uk>
Sender: news@boulder.Colorado.EDU
Reply-To: eddy@boulder.Colorado.EDU (Sean Eddy)
Organization: University of Colorado, Boulder
Lines: 26

In article <2863@bath63.ux63.bath.ac.uk> bs_wab@ux63.bath.ac.uk (Bains) writes:
>iii) I was not all that interested in viruses themselves anyway, but in
>viroids, which appear to be self-replicating RNAs requiring only
>RNA precursors to reproduce. The RNA strand is both message and polymerase.

This is (unfortunately for the romantics of the "RNA world" hypothesis)
not correct. The replicase involved in viroid replication has not
been identified, to my knowledge. 
The known RNA catalytic activity of viroid RNAs
is limited to self-cleavage and such. (Unless you know
of something quite recent -- but here in the land of Tom Cech, 
such a discovery would have left the place in chaos...)

The only RNA-based "polymerase" in the literature so far is a derivative
of the _Tetrahymena_ self-splicing group I intron, which is capable
of rearranging ribooligonucleotides to a small extent
to make both longer and shorter products. 

- Sean Eddy
- Molecular/Cellular/Developmental Biology; U. of Colorado at Boulder
- eddy@boulder.colorado.EDU		!{hao,nbires}!boulder!eddy	
-
- "But the scientist is intensely religious -- he is so religious
-  that he will not accept quarter-truths, because they are an 
-  insult to his faith."
-                       - Sinclair Lewis, in _Arrowsmith_