Summary
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.
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Communicated by Ch. Auerbach
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Boncinelli, E., Furia, M. Patterns of reversion to bobbed condition of magnified bobbed loci in D. melanogaster . Molec. Gen. Genet. 176, 81–85 (1979). https://doi.org/10.1007/BF00334298
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DOI: https://doi.org/10.1007/BF00334298