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From: gerryg@laidbak.UUCP
Newsgroups: sci.bio
Subject: Re: information content of DNA
Message-ID: <917@laidbak.UUCP>
Date: Mon, 6-Apr-87 21:28:51 EST
Article-I.D.: laidbak.917
Posted: Mon Apr  6 21:28:51 1987
Date-Received: Thu, 9-Apr-87 02:38:26 EST
References: <2840@ecsvax.UUCP> <11189@teknowledge-vaxc.ARPA> <978@aecom.UUCP> <2844@ecsvax.UUCP> <7659@ut-sally.UUCP> <425@haddock.UUCP>
Reply-To: gerryg@laidbak.UUCP (Gerry Gleason)
Organization: LAI Chicago
Lines: 38

In article <425@haddock.UUCP> johnc@haddock.ISC.COM.UUCP (John Chambers) writes:
>I wonder if anyone has ever built a computer with the possibility of multiple
>"reading frames".  Consider an 8-bit memory, but a 16-bit instruction size.
>If you start executing at address A and at A+1, you get two possibly very
>different programs.  Can any real-life processors do this?  It happens
>with DNA quite often.

When I first understood that a coded DNA sequence could mean different things
when decoded in different "phases", I thought about this connection to
computer programs and data.  It's not hard to see that this is a characteristic
of the software, not the hardware.  I think of it as a compression technique,
once you have a program or data structure, you can look for ways of
compressing it by folding it back on itself.  That is look for places where
a piece of code or data is duplicated in another, unintended place.  The
original copy can be deleted, and references to it refered to the new location.
Of course you can get more fancy by rearanging or modifying things in a way
that doesn't effect function to create a redundancy that can be deleted.
Its probably not a very productive way to save your computer resources, but
it is interesting to think about.

In the case of DNA, there are several things that I wonder about.  First, how
does the cell keep non-sensical things from getting expressed.  I know there
is a lot of DNA devoted to "control" functions, but its hard to beleive that
every possible reading of a DNA sequence either doesn't get expressed, or is
necessary to (or at least not dangerous for) the organism.  Another thing,
when DNA sequences get rearanged in reproduction, new sequences are
produced and other destroyed by this process.  How can a cell survive this
with its genetic information intact?  Or is it that we never see the mistakes?
And then, the transcription process can't be 100% reliable, but there's a lot
of information in the DNA of most organisms; there must be mistakes.  How
does the organism cope with this?  Is it just redundancy?  Or is there some
kind of repair mechanism that puts an almost right sequence back together?

Well, I'm not a biologist, but it seems to me that these are interesting
questions, and I suspect that we haven't gotten very close to answering
them.

gerry gleason