Clustering of transfer RNAs by cell type and amino acid specificity.

Procaryotic and eucaryotic transfer RNA sequences are distinct at the 0.5% probability level as demonstrated by permutation testing. Moreover, within each cell type, transfer RNA sequences of different amino acid acceptor classes are distinct at the 0.1% level. We propose that the latter finding reflects sets of nucleotides, other than the anticodons themselves, that specifically relate the transfer RNAs to their respective amino acids. The utility of permutation testing is emphasized by the additional information this study provides compared to that of Holmquist et al. (1973), using the same data set.