Mobilization of autonomous and non-autonomous transposons. Transcription from autonomous transposons is driven by either an upstream promoter (i) or by the IR (ii) (1a). Non-autonomous transposons comprising loss-of-function mutations (indicated by lightning bolt) are unable to make a functional transposase (1b). mRNA from the autonomous transposon is exported to the cytoplasm (2), translated into functional transposase (3), which is transported into the nucleus (4). The transposase recognizes both autonomous and non-autonomous transposons (5) leading to transposition of both (6).