On codon reassignment.
Schultz and Yarus (J. Mol. Biol. 235:1377-1380, 1994) have proposed that reassignment of codons in the genetic code passes through a stage in which the codons are ambiguously translated. In contrast we state that such ambiguity would be deleterious, and that, to be reassigned, a codon, together with the tRNA that translates the codon, must first disappear from coding sequences, after which a tRNA appears with a mutated anticodon, and this enables the codon to reappear with a changed meaning. In the case of a stop codon, the relevant release factor must change so as to recognize it.
Osawa
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Jukes
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D003062:Codon; D005815:Genetic Code / Q000235:genetics*; D012343:RNA, Transfer / Q000235:genetics
D003062:Codon; D012343:RNA, Transfer