Based on the revised wobble rules specific to eukaryotes [Guthrie & Abelson, 1982] (Table 3.1), I anticipated finding 46 distinct tRNA species in the C. elegans collection. Indeed, we found precisely 46 families, plus a single selenocysteine-inserting (SeC) tRNA. Interestingly, the 46-family prediction was based on an incomplete set of tRNAs from S. cerevisiae, which turned out to have only 42 tRNA species [Percudani et al., 1997,Hani & Feldmann, 1998]. The missing four families were accounted for by known differences in anticodon modifications in existing tRNAs which could expand base pairing ability and compensate for the absent species [Percudani et al., 1997,Hani & Feldmann, 1998]. Almost no direct modification data for C. elegans tRNA anticodons exist, but based on the full complement of tRNAs found, C. elegans tRNAs are expected to be very typical of eukaryotic tRNAs.
The most comprehensive collection of tRNA genes, the Sprinzl tRNA database [Steinberg et al., 1993], had formerly identified 42 total C. elegans tRNAs falling into 35 families. Thus, 12 new families were identified based on the completed genome sequence.