Har-P is a short P-element variant that collaborates with P transposase to induce strong gonadal dysgenesis.

This study demonstrates that a short version of the P-element transposon exists naturally and acts as the main genetic agent causing the fertility syndrome of gonad dysgenesis. The data help explain the variability of the gonad dysgenesis phenotype in different drosophila strains and explains why the Harwich strain is the tester strain that drives the strong GD effect.