Evidence for a host role in regulating the activity of transposable elements in Drosophila melanogaster: the case of the persistent instability of Bari 1 elements in Charolles stock.

In most reports in which the activity of numerous Drosophila transposon families has been studied, only a subset of the families tested appears mobile. A comparison of these data shows that there are no transposons inherently more unstable than others and suggests that host factors regulate the activity of transposable elements. Consistent with this conclusion are the properties of Bari 1 elements, which are the only ones of the 14 families tested to be unstable in Charolles stock. Instability is persistent over 53 generations and appears to affect recurrent insertion sites.