The Historical Factor: The Biosynthetic Relationships Between Amino Acids and Their Physicochemical Properties in the Origin of the Genetic Code |
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Authors: | Massimo Di Giulio Mario Medugno |
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Institution: | (1) International Institute of Genetics and Biophysics, CNR, Via G. Marconi 10, 80125 Naples, Napoli, Italy, IT;(2) Centro di Ricerca per il Calcolo Parallelo e Supercalcolo, CNR, Via Diocleziano 328, 80124 Naples, Napoli, Italy, IT |
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Abstract: | Two forces are in general, hypothesized to have influenced the origin of the organization of the genetic code: the physicochemical
properties of amino acids and their biosynthetic relationships. In view of this, we have considered a model incorporating
these two forces. In particular, we have studied the optimization level of the physicochemical properties of amino acids in
the set of amino acid permutation codes that respects the biosynthetic relationships between amino acids. Where the properties
of amino acids are represented by polarity and molecular volume we obtain indetermination percentages in the organization
of the genetic code of approximately 40%. This indicates that the contingent factor played a significant role in structuring
the genetic code. Furthermore, this result is in agreement with the genetic code coevolution hypothesis, which attributes
a merely ancillary role to the properties of amino acids while it suggests that it was their biosynthetic relationships that
organized the code. Furthermore, this result does not favor the stereochemical models proposed to explain the origin of the
genetic code. On the other hand, where the properties of amino acids are represented by polarity alone, we obtain an indetermination
percentage of at least 21.5%. This might suggest that the polarity distances played an important role and would therefore
provide evidence in favor of the physicochemical hypothesis of genetic code origin. Although, overall, the analysis might
have given stronger support to the latter hypothesis, this did not actually occur. The results are therefore discussed in
the context of the different theories proposed to explain the origin of the genetic code.
Received: 10 September 1996 / Accepted: 3 March 1997 |
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Keywords: | : Genetic code theories — Measurement of history — Polarity — Molecular volume — Distance indices — Minimization percentage — Parallel algorithms |
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