Suppression of ribosomal RNA genes inDrosophila melanogaster

Abstract

SUMMARYThe rDNA of fiveYchromosome mutants was examined with respect to their insert free (In−) repeat type multiplicity. The In− repeat number of each mutant was correlated with its hemizygousbobbedphenotype and additivity with anXNObobbed(bb) mutant. Four of these mutants showed a direct relationship between their In− frequency, hemizygousbbphenotype and additivity tests. A fifth mutant,bb1–4, had a sufficient number of In− repeats to ensure viability to the late pupal stage and show additivity; however, the In− repeats genetically behaved as a complete rDNA deletion. Possible mechanisms resulting in the suppression of thebb1–4In− repeats are discussed.