Selective replication of ribosomal DNA repeats after loss of the abnormal oocyte phenotype in Drosophila melanogaster.

Drosophila melanogaster females homozygous for the abnormal oocyte mutation produce a large excess of female offspring when crossed with XY/0 males. After several generations in abo homozygous stock, this maternal effect is no longer observed. The disappearance of the abo phenotype is coupled with an increase in the amount of DNA coding for rRNA (rDNA). We have used restriction endonuclease analysis of total DNA extracted from adult females and from single female larval brains to investigate the molecular organization of rDNA before and after the loss of abo phenotype. The rDNA increase is associated with variations of the restriction pattern of the nontranscribed spacer, probably due to a selective increase of rDNA repeats.