IDENTIFICATION OF THE YEAST DNA SEQUENCES THAT CORRESPOND TO SPECIFIC TYROSINE-INSERTING NONSENSE SUPPRESSOR LOCI

There are 8 unlinked genes for yeast tyrosine tRNA. Nonsense suppressors previously were isolated at each of the 8 loci, and these loci were genetically mapped. It was demonstrated by RNA-DNA hybridization that the genes are physically located on 8 different EcoRI restriction fragments. The present report cross-correlates the set of tyrosine-inserting suppressor loci with the set of tRNATyr-hybridizing restriction fragments. This cross-correlation was achieved for 6 of the 8 loci by analyzing the meiotic and mitotic linkage between the tyrosine-inserting suppressors and the genetic determinants of naturally occurring size variants of the tRNATyr-hybridizing restriction fragments. Now that individual suppressor loci have been identified with specific DNA fragments, it should be possible to analyze the phenotypes of these mutant genes in terms of their DNA sequences. The method by which these assignments were made also offers a new approach to the general problem of correlating genes with restriction fragments; it is particularly suited to organisms with powerful genetic systems where hybridization to chromosome spreads in situ is impractical.