Spontaneous changes in Drosophila melanogaster transposable elements and their effects on fitness

Twenty-eight spontaneous alterations modifying the hybridization banding pattern of six families of transposable elements (297, Foldback, copia, jockey, P and hobo) have been fixed in a set of mutation-accumulation lines of Drosophila melanogaster. Their effect on fitness has been studied by competition with the original pattern. Most alterations affecting transposable elements were shown to be rearrangements with no detectable effect on fitness, showing that spontaneous transposable element mutations mainly generate minor fitness mutations.