Position-effect variegation in Drosophila melanogaster X chromosome inversion with a breakpoint in a satellite block and its suppression in a secondary rearrangement

Chromosoma. 1997 Dec;106(8):520-5. doi: 10.1007/s004120050274.


In(1LR)pn2a is a pericentric inversion with a euchromatic breakpoint in the 2E polytene region and a heterochromatic breakpoint in the right arm of the X chromosome. It is associated with position-effect variegation (PEV) of the pn, wapl, Pgd and other vital loci of the 2E region, which are relocated near the bulk of the X heterochromatin. Cytological analysis showed that the rearrangement brings the 1A-2E euchromatic segment directly into contact with a major portion of the h34 block, a heterochromatic region that is positively stained by the N-banding technique and contains the AAGAG satellite sequences. Molecular cloning revealed the presence of a new junction between euchromatin and AAGAG satellite sequences and demonstrated that the euchromatic breakpoint of In(1LR)pn2a lies in the vinculin gene. In the X ray-induced secondary rearrangement In(1LR)r30, consisting of a pericentric inversion superimposed on In(1LR)pn2a, the h34 material remains associated with the 2E region but is separated from the rest of the X heterochromatin. In this case, the pn, wapl and Pgd loci no longer variegate, suggesting that the satellite-containing h34 region is not able per se to induce detectable PEV on the adjacent euchromatic genes.

MeSH terms

  • Animals
  • Chromosome Breakage*
  • Chromosome Inversion*
  • DNA, Satellite / genetics*
  • Dosage Compensation, Genetic
  • Drosophila melanogaster / genetics*
  • Heterochromatin / chemistry
  • Heterochromatin / genetics
  • Suppression, Genetic*
  • X Chromosome / genetics*


  • DNA, Satellite
  • Heterochromatin