Characterization of the tilt (tt) phenotype in Drosophila melanogaster.

In the early 20th century, Calvin Bridges and Thomas Morgan identified a number of spontaneous mutations that displayed visible phenotypes in adult flies and subsequent analysis of these mutations over the past century have provided fundamental insights into subdisciplines of biology such as genetics, developmental, and cell biology. One of the mutations they identified in 1915 was named tilt ( tt ) and was described by Bridges and Morgan as having two visible phenotype characteristics in the wing. The wings were "held out at a wider angle from the body" and had a break in wing vein L3. Subsequent analysis of the tilt phenotype identified another phenotype: the wings were missing a varying number of campaniform sensilla on L3. Though Bridges and Morgan provided an ink drawing of the wing posture phenotype, only the vein and campaniform sensilla loss images have been published. Here we confirm and document the tilt phenotypes that have been previously described. We also show the penetrance of these phenotypes: the vein break and the distinct outward wing posture have decreased since its discovery.