title: Patterns of reversion to bobbed condition of magnified bobbed loci in D. melanogaster.
abstract: The number of genes coding for the ribosomal RNA (rDNA) can increase in D. melanogaster by means of a process called magnification. In this way, a partial deletion in this locus, termed bobbed, can reach a wild type condition. A newly magnified locus, in turn, reverts to a deficient bobbed condition if it is kept in a phenotypically wild type genotype for several generations. We studied bobbed loci at different magnification steps, analysing their behaviour through the reversion process and the way they carry out a second round of magnification. Results based on the analysis of the reversion process led to the conclusion that magnification consists of a progressive integration into the bobbed locus of free rDNA copies. Moreover, evidence is supplied that the extent of this integration affects the way a reverted locus goes through a second magnification cycle. The extensive characterization of reverted bobbed loci lends substantial support to the extra copies model of rDNA magnification.
mesh_terms: D000818:Animals; D004331:Drosophila melanogaster / Q000235:genetics*; D005784:Gene Amplification; D005796:Genes; D009154:Mutation; D010641:Phenotype; D012335:RNA, Ribosomal / Q000235:genetics*
chemical_list: D012335:RNA, Ribosomal