Homozygous females are poorly fertile laying only a small number of eggs, of which up to 65% do not develop, hemizygous females are sterile. Extreme contraction of all appendages under anaesthesia. Embryos display defects in the organisation of axon pathways, fasciculation of segmental and intersegmental nerves is altered. Longitudinal tracts and commissures are also affected, the cuticle is not. Appendage contraction, low viability and fertility phenotypes are enhanced by one extra dose of the Sh complex. Two doses of Sh complex are lethal. Individuals also have a defective nervous system. Mutant females give rise to significantly more female progeny than male when crossed to wild type males, this suggests a zygotic rescue of a maternal deficit.

A high percentage of eggs laid by homozygous females fail to develop. Homozygotes have defective learning performance, fail to perform normally in associative learning paradigm. All males and most females are lethal when two extra doses of Sh are present, lethality predominantly occurs during embryogenesis and early larval stages. The few escaper females (less than 1% viability) have an inflated abdomen and die a few hours after eclosion. Individuals exhibit a reduction in wing surface at 29^oC. Strong contraction of appendages when anaesthetised (the narcotic agent used is irrelevant for the mutant phenotype): twisting of neck and abdomen, wings held up or down and extrusion of the proboscis. One extra dose of Sh, Dp(1;3)JC153, potentiates the tta phenotype. Effects of anaesthesia last 50% longer than in normal flies. After recovery from the anaesthesia individuals are apparently normal.

Viable, but shows tetanization under anaesthesia. Unable to learn. tta individuals are sensitive to extra doses of the haplo-lethal region of the Sh complex, males with two doses are lethal.

Viable, but shows tetanization under anaesthesia. Unable to learn. tta males with two doses of the Shaker gene complex are lethal.