Inserted sequence in the mitochondrial 23S ribosomal RNA gene of the yeast Saccharomyces cerevisiae.

Summary The sequence organization of the yeast mit-DNA region carrying the large ribosomal RNA gene and the polar locus was examined. Hybridization studies using rho^- deletion mutants and electron microscopy of the heteroduplexes formed between 23S rRNA and the appropriate restriction fragments, lead to the conclusion that the 23S rRNA¹ gene of the ⁺ strains is split by an insertion sequence of 1,000–1,100 bp. In contrast, no detactable insertion was found in the 23S rRNA gene of the ^- strains. The size and the location of the insert found in the 23S rRNA gene of the ⁺ strains appear to be identical to those of the sequence which had previously been found to characterize the difference (at the locus) between the mitDNA of the wild type strains carrying the ⁺ or ^- alleles (Jacq et al., 1977).