INTRODUCTION OF A TRANSPOSABLE COPY OF TH E RETROTRANSPOSON GYPSY INDUCES GENETIC INSTABILITY IN A STABLE DROSOPHILA-MELANOGASTER STRAIN

A previously described system of a Drosophila melanogaster mutative st rain (MS), which originates from a stable strain (SS), is characterize d by genetic instability caused by transpositions of the retrotranspon son gypsy. New unstable strains were obtained by microinjections of th e gypsy transposable copy into SS embryos. In situ hybridization exper iments revealed amplification and active transposition of gypsy in SS derivatives. At the same time, introduction of the a gypsy transposabl e copy into another stable strain (208) did not lead to appearance of genetic instability. Genetic instability in the MS system is apparentl y induced by a combination of two factors: the presence of a gypsy tra nsposable copy and mutation(s) in the gene(s) regulating its transposi tions.