It has been speculated that U33 is necessary for forming of C.maltosa possessing this type of tRNA Ser CAG also the U-turn structure of the anticodon loop in all tRNAs suggested that the URA3 gene inactivated due to the reported so far (Quigley and Rich, 1976 ; Sprinzl et al., translation of CUG as serine was rescued by a slight 1996) . Moreover, the nucleotide at position 37, 3Ј-adjacent incorporation of leucine into the polypeptide, which to the anticodon CAG, is 1-methyl guanosine (m 1 G) in demonstrated that the tRNA charged with multiple almost all tRNA Ser CAGs except for that of C.cylindracea amino acids could participate in the translation. These (A37), while all the serine tRNAs in fungi corresponding findings provide the first evidence that two distinct Introduction Normanly and Abelson, 1989; Shimizu et al., 1992; McClain, 1993; Schimmel et al., 1993) . This line of study The universality of the genetic code was once considered began with the artificial conversion of leucine tRNA of to be one of the essential characteristics of life, which led Escherichia coli to serine tRNA by Abelson's group 10 to the conception of the 'frozen accident theory'. This years ago (Normanly et al., 1986) . Recently, tRNA identity theory proposes that all extant living organisms use the elements of Saccharomyces cerevisiae leucine tRNA were universal genetic code, which was born by accident and elucidated using unmodified variants synthesized by T7 'frozen', and that they originate from a single, closely RNA polymerase (Soma et al., 1996) , indicating that in interbreeding population (Crick, 1968) . However, in recent addition to the discriminator base, A73, the second letter years a number of non-universal genetic codes have been of the anticodon, A35, and the nucleotide 3Ј-adjacent to reported in various non-plant mitochondrial systems, as the anticodon, m 1 G37, are important for recognition by well as in several nuclear systems (reviewed in Osawa leucyl-tRNA synthetase (LeuRS). The majority of Candida et al., 1992; Osawa, 1995) , which contradict the frozen tRNA Ser CAGs have A35 and m 1 G37, while the discriminaccident theory.