Abstract Definite patterns of recognition of synonym codon triplets have been observed for transfer RNA (tRNA). These same patterns should occur in mutant tRNA, which behaves as missense or nonsense suppressor RNA. Thus the codon triplet recognition patterns of suppressor RNA's are predictable and should include several patterns which hav not yet been discovered. The name Topaz is proposed for one of these, the suppressor which places tyrosine at the nonsense triplet UAA.