The zebrafish genome contains two distinct selenocysteine tRNA([Ser]Sec) genes

The zebrafish is widely used as a model system for studying mammalian devel opmental genetics and more recently, as a model system for carcinogenesis. Since there is mounting evidence that selenium can prevent cancer in mammal s, including humans, we characterized the selenocysteine tRNA([Ser]Sec) gen e and its product in zebrafish, Two genes for this tRNA were isolated and s equenced and were found to map at different loci within the zebrafish genom e. The encoding sequences of both are identical and their flanking sequence s are highly homologous for several hundred bases in both directions. The t wo genes likely arose from gene duplication which is a common phenomenon am ong many genes in this species, Tn addition, zebrafish tRNA([Ser]Sec) was i solated from the total tRNA population and shown to decode UGA in a ribosom al binding assay, (C) 1999 Federation of European Biochemical Societies.