THE MOLECULAR-BASIS OF I-R HYBRID DYSGENESIS IN DROSOPHILA-MELANOGASTER - IDENTIFICATION, CLONING, AND PROPERTIES OF THE I-FACTOR

Two mutations of the white-eye gene, which arose in flies subject to I-R hybrid dysgenesis were analyzed. These mutations are associated with insertions of apparently identical 5.4 kilobase sequences, which were cloned. These insertions apparently are copies of the I factor controlling I-R hybrid dysgenesis. The I factor is not a member of the copia-like or fold-back classes of transposable elements and has no sequence homology with the P factor that controls P-M dysgenesis. All strains of D. melanogaster contain I-factor sequences. Those present in reactive strains must represent inactive I elements. I elements have a remarkably similar sequence organization in all reactive strains and are located in peri-centromeric regions. Inducer strains appear to contain both I elements, located in pericentromeric regions, and 10-15 copies of the complete I factor at sites on the chromosome arms.