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From: werner@aecom.UUCP
Newsgroups: sci.bio
Subject: Re: information content of DNA
Message-ID: <1018@aecom.UUCP>
Date: Wed, 8-Apr-87 23:28:11 EST
Article-I.D.: aecom.1018
Posted: Wed Apr  8 23:28:11 1987
Date-Received: Sat, 11-Apr-87 13:55:57 EST
References: <2840@ecsvax.UUCP> <11189@teknowledge-vaxc.ARPA> <978@aecom.UUCP> <430@haddock.UUCP>
Organization: Albert Einstein Coll. of Med., NY
Lines: 33
Summary: Reading frames

In article <430@haddock.UUCP>, johnc@haddock.UUCP (John Chambers) writes:
> In article <1010@aecom.UUCP> diaz@aecom.UUCP (Dizzy Dan) writes:
> >In article <425@haddock.UUCP>, johnc@haddock.UUCP (John Chambers) writes:
> >> Granted, it is very rare that all six readings actually code for something
> >
> >Forget rare, there ain't no such animal. Although multiple reading
> >frames have been observed in phage, and transcription from complementary
> >strands observed in a variety of organisms (most recently, mice) there
> >is no documented example of anywhere near the six possible readings
> >coding for functional polypeptides. 
> 
> Come now, isn't it a tad early to make such a declaration? 

	It is quite probable that an organism using all 6 reading
frames in a given DNA sequence will never be found. Two is used
quite often (usually opposite strands, including genes within
an intron, rather than overlapping, which is also stretching the
point).
	Three is only observed once, and that almost doesn't count.
In the splicing of Polyoma T-antigens, the 3' splice site of the
respective introns, fall into 3 reading frames.  Small T-antigen
encounters a stop codon several amino acids later, but large T
goes on for quite some distance.
	The reason that this is cheating is that the first part
(95%, 50%, 30%) of each transcript is absolutely identical -
there is only one promoter.  It is only the 3' end of the genes
that are in all three reading frames.

-- 
			      Craig Werner (MD/PhD '91)
				!philabs!aecom!werner
              (1935-14E Eastchester Rd., Bronx NY 10461, 212-931-2517)
               "Time flies when you're streaking out N. gonorrheae."