DELETIONS AND AMPLIFICATIONS OF TANDEMLY ARRANGED RIBOSOMAL 5S GENES INTERNAL TO A P-ELEMENT OCCUR AT A HIGH-RATE IN A DYSGENIC CONTEXT

We observed unusual kinds of rearrangements within tandemly clustered 5S genes internal to a P element in dysgenic context. Rearranged P tra nsposons, initially containing eight 5S genes, were found to display d iscrete numbers of 5S genes, from 4 up to 17 units. Precise deletions and amplifications occurred at a high rate (40%), at both original and new insertion sites. These events can be explained by a 'cut and past e' transposition model. Possible links between rearrangements due to d ysgenic-like processes and concerted evolution are discussed.