Increase of rDNA redundancy in bb females of Drosophila melanogaster.

The purpose of this work was to analyze the difference between males and females with respect to rDNA magnification. To study eventual rDNA variations in females aYbb chromosome was chosen since it can magnify in males but not show phenomena of rDNA dosage compensation. The authors have observed an increase of rDNA pertaining to the Ybb chromosome in females of XXNO-/Ybb genotype with respect to the same Ybb chromosome studied in XXbb+/Ybb females. This non-inheritable rDNA increase cannot be explained in terms of compensatory increase reported in X/O males nor can it fit in the magnification scheme. The possibility might be entertained that some mechanism is missing in females which cannot complete a magnification cycle. The rDNA increase that we called rDNA magnification in males occurs in the germ line and in the soma, whereas the evidence, here reported, suggest that magnification in females occurs only in the soma.