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@make(letterhead,Phone"497-4430",Who"John McCarthy",Logo,Old,Department CSD)
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Professor Douglas Hofstadter
Department of Computer Science
University of Indiana
Bloomington, Indiana  47401
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@greeting(Dear Doug:)
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	I liked your March Scientific American column.  The isolation of
the logical aspects of the encoding from the chemical aspects was
illuminating.  However, a question remains.

	You have shown that the DNA to protein code is arbitrary, since
the (anticodon, DHU loop) coding is arbitrary in the tRNA.  However, it
is interesting to ask whether the (DHU loop, amino acid) coding is also
arbitrary or is somehow determined by the chemistry.  If it is determined,
then the complication is explained if there is some reason why the
(DNA, amino acid) coding should be arbitrary.

	No need to answer personally if you answer in your column.
@end(body)
Best regards,




John McCarthy
Professor of Computer Science