Heritable somatic excision of a Drosophila transposon.

A mutation in the white gene of Drosophila mauritiana that results from insertion of the transposable element mariner is genetically unstable in both germ cells and somatic cells. Somatic instability is indicated by the occurrence of animals having mosaic eyes with patches of pigmented cells on a peach-colored background. Normally uncommon, the frequency of mosaicism is so greatly enhanced in a particular mutant strain that virtually every animal in the strain is an eye-color mosaic. The molecular basis of the mosaicism is the excision of the mariner element from its location in the DNA of the white gene in somatic cells. The phenomenon results from a single dominant genetic factor located in chromosome 3. Genetic control over the excision of transposable elements may play a role in determining the persistence of transposable elements in the genome.