Analysis of disproportionate replication of ribosomal DNA in Drosophila melanogaster by a microhybridization method.

A microhybridization technique is described which requires only 1% of the starting material normally needed for filter-bound methods. Employing this technique, we have investigated the disproportionate replication (compensation) of ribosomal DNA in larval and adult stages of two strains of Drosophila melanogaster. Both stages of the Oregon R strain demonstrate XO compensation while neither stage of Canton S shows a significant elevation of ribosomal DNA content in XOs. It is demonstrated that the lack of disproportionate replication in the latter strain does not result from the absence of the genetic site cr+ which normally controls this process.