![]() ![]() Further, any codon reassignment would affect the anticodon of the tRNA corresponding to that changed codon - often interacting with more than one codon and dependent on recognition by the amino acyl-tRNA synthetase for attachment of the correct amino acid.Īn alternative explanation for the conundrum ![]() Remember changing the assignment in one codon would affect all proteins using that codon, in contrast to a mutation of a single codon in a single protein to a different amino acid. This is consistent with the “frozen accident” idea (originally proposed by Crick) - once the genetic code was to a certain stage it become frozen because changes would have been lethal. In the generally small and isolated mitochondrial genomes the selective pressure for variation would seem to have been to reduce the number of tRNAs needed to decode the mRNA. The genetic code today is the same in almost all organisms, and the variations in the exceptional species are only minor. Is selective pressure to minimize amino acid changes likely to have been important in the evolution of the genetic code?
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