Transgenic direct terminal repeats of Dissociation ( Ds ) produce chromosomal breakage in maize

Barbara McClintock recognized transposable elements originally by the movement of a site of chromosomal breakage, a genetic element called Dissociation ( Ds ) that was induced to break or transpose by another element she called Activator . The chromosome breaking version, when analyzed on the molecular level was one transposon inside another. It is now known that transposition involving transposon termini in non-standard orientation with reference to each other results in chromosomal breakage. Here we used engineered transposon ends together with a phenotypic marker to cause targeted chromosomal breaks. The results indicate that engineered direct orientation of the naturally inverted repeats of Dissociation can cause chromosomal breakage at the transgenic sites of insertion.