Serine tRNA (tRNA-Ser), predicted by tRNAscan-SE analysis;
i6A37 modification is catalyzed by Mod5p; can mutate to suppress amber or ochre nonsense mutations; suppressor mutant alleles are recessive lethal and can only be maintained when an additional wild-type copy of the gene is present, because SUP61 encodes the only tRNA species that can decode UCG codons