gfA^PΔ41 flies perform no differently to wild-type flies in terms of flight, olfactory behavior, and in visual tests (although there is a slight difference in phototaxis assays compared to wild-type flies). However, in contrast to wild-type flies, these flies fail to jump in response to a lights-off stimulus.

gfA^PΔ41 flies have a defect in the jump circuit between the peripherally synapsing interneuron (PSI) branch of the giant fiber and the dorsal lateral muscle (DLM) motor neuron. This is demonstrated by intracellular recordings of DLMs following giant fiber stimulation; while the DLMs of wild-type flies can follow stimulation frequencies of up to 100 Hz, gfA^PΔ41 DLMs respond reasonably well at 1 Hz, although show an abnormally long latency. At 10 Hz the mutant DLM responses start to fail and show little response at all at 100 Hz. The defects are specific to the synapses between the PSI and DLM motor neurons as the tergotrochanteral muscles are able to follow the giant fiber stimulation at 100 Hz without any problem.

The tergotrochanteral muscle of gfA^PΔ41 flies responds to low-strength electrical stimulation, which activates the elements presynaptic to the giant fiber, which in turn activate the giant fiber, with the short-latency response seen in wild-type flies, but fails to show the long-latency response.