Instability at the bobbed locus following magnification in Drosophila melanogaster.

Newly magnified bobbed loci, combined with bb+ or bbo loci, are in certain cases unstable. This may lead either to a reversion to the original bobbed mutation, or to lethal bobbed mutations. We name this instability “modification”. Modification occurs very early during the first divisions following fecondation of eggs, in embryos heterozygous for a magnified bobbed locus and a bb+ or bbo locus. The phenomenon of modification is consistent with the model proposed by Ritossa (1972) to account for the phenomenom of magnification.