Читать книгу Astrobiology - Charles S. Cockell - Страница 113

How did the codon table evolve? It is instructive to notice that the amino acids are bunched together in the table. This has not gone unnoticed. One early hypothesis was that this arrangement leads to the minimization of errors. If the third location in the codon, which has a certain degree of “wobble,” changes, then the amino acid in the final protein is not changed. Mathematical models show that the codon table, as constituted, can achieve this error minimization. There are also other intriguing observations. For example, arginine is able to bind directly to the RNA codes represented by the codons in the table, without the transfer RNAs. The same is true for isoleucine. Could these amino acids have once bound directly to the RNA with the transfer RNA molecules becoming adaptors between the RNA and the amino acids later? It is possible that none of these ideas is mutually exclusive. Error minimization and direct associations between codons and amino acids and other factors may all have played a role in evolving the table early in the history of life.