EVIDENCE FOR AN INDUCIBLE REPAIR-RECOMBINATION SYSTEM IN THE FEMALE GERM-LINE OF DROSOPHILA-MELANOGASTER .1. INDUCTION BY INHIBITORS OF NUCLEOTIDE SYNTHESIS AND BY GAMMA-RAYS

In the I-R system of hybrid dysgenesis in Drosophila melanogaster, the transposition frequency of I factor, a LINE element-like retrotranspo son, is regulated by the reactivity level of the R mother. This reacti vity is a cellular state maternally inherited but chromosomally determ ined, which has been shown to undergo heritable, cumulative and revers ible changes with aging and some environmental conditions. We propose the hypothesis that this reactivity level is one manifestation of an i nducible repair-recombination system whose biological role might be an alogous to the SOS response in bacteria. In this paper, we show that i nhibitors of DNA synthesis and gamma rays enhance the reactivity level in a very similar way. This enhancement is heritable, cumulative and reversible.