Here we re-examine the biochemical basis of this theory to test the validity of its statistical support. We show that the theory's definition of ''precursor-product'' amino acid pairs is unjustified biochemically because it requires the energetically unfavorable reversal of steps in extant metabolic pathways to achieve desired relationships. In addition, the theory neglects important biochemical constraints when calculating the probability that chance could assign precursor-product amino acids to contiguous codons. A conservative correction for these errors reveals a surprisingly high 23% probability that apparent patterns within the code are caused purely by chance. Finally, even this figure rests on post hoc assumptions about primordial codon assignments, without which the probability rises to 62% that chance alone could explain the precursor-product pairings found within the code. Thus we conclude that coevolution theory cannot adequately explain the structure of the genetic code.

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GENVIEW: and GENCODE: are tools for testing the adaptive nature of a genetic code under different assumptions about patterns of genetic error and the nature of amino acid similarity. GENVIEW: provides a user friendly, point-and-click interface by which a user may reproduce and extend analysis of the adaptive properties of the standard genetic code or any of its secondary derivatives. GENVIEW: is a graphical user interface (GUI) program which runs on Linux, Unix and Microsoft Windows platforms and is based on the GTKf + toolkit. GENVIEW: outputs ASCII configuration files which are interpreted by GENCODE: to perform an analysis. GENCODE: is available for the same platforms as GENVIEW.