Re: Information: Brad's reply (was Information: a very

Brian D Harper (
Wed, 24 Jun 1998 20:46:02 -0400

At 09:23 PM 6/23/98 -0500, Glenn wrote:

>At 10:17 PM 6/23/98 +0800, Brad Jones wrote:
>>I think there are two major problems with your reasoning.
>>1. you are assuming that the information content of DNA is best
>>modeled as a information source. As I will show below this is not the
>>case and by doing so you will not produce any informative results.
>>2. Your analysis of DNA as an information source is also incorrect
>>and your results are misleading.
>>The main mistake that you made was to assume that DNA is a "zero
>>memory" source. A zero memory source outputs symbols that do not
>>depend on the previous symbols; this is not the case with DNA.


>You are using a 10th degree Markov chain and that is not what DNA is. Brian
>would you care to comment on this?

I don't know what to say except to repeat what Yockey says in
his book. In section 5.1.3 he states that the DNA-mRNA-protein
system is discrete, memoryless and unconstrained. These terms
are defined as follows:

#discrete memoryless source#: "one in which there are no restrictions
or intersymbol influence between the letters of the alphabet."

#discrete memoryless channel#: one in which "the response of the
channel to the input letters is independent of previous letters"

#unconstrained channel#: one that "allows input symbols to be
transmitted in any sequence"

As an interesting sidelight to this, Yockey mentions in this
same section an argument given by Monod as to why protein
sequences are due to chance. The argument goes roughly like
this. First you note that you are unable to predict an
amino acid in the sequence knowing what the neighboring
amino acids are. From this you conclude that the sequence
is random and from this that it must be due to chance.
A clever argument the refutation of which is not particularly
obvious. Yockey's refutation is simply that the inability
to predict an amino acid from its neighbors reflects only
the fact that there is no intersymbol influence. So, Monod
was apparently done in by a faulty analogy with natural
languages which do have intersymbol influence.

Brian Harper
Associate Professor
Applied Mechanics
The Ohio State University

"It appears to me that this author is asking
much less than what you are refusing to answer"
-- Galileo (as Simplicio in _The Dialogue_)