Expression of one copy of Hsap\YARS^{153-156delVKQV.Scer\UAS} under the control of either Scer\GAL4^Act5C.PU or Scer\GAL4^tub.PU results in normal adult offspring. Expression of two copies of Scer\GAL4^Act5C.PU results in either lethality or partial lethality depending on the strength of the line.

Pan-neuronal expression of Hsap\YARS^{G41R.Scer\UAS} under the control of Scer\GAL4^elav.PU has no effect on motor performance in negative gravitaxis assays.

No obvious degeneration is observed when Hsap\YARS^{G41R.Scer\UAS} is expressed under the control of Scer\GAL4^nSyb.PS.

Jumping and flying defects are seen when one strong and one weak copy of Hsap\YARS^{G41R.Scer\UAS} is expressed under the control of Scer\GAL4^Act5C.PU.

Flies expressing one copy of Hsap\YARS^{G41R.Scer\UAS} under the control of Scer\GAL4^Act5C.PU show normal behaviour in a negative geotaxis climbing assay. However, flies expressing two copies of Hsap\YARS^{G41R.Scer\UAS} under the control of Scer\GAL4^Act5C.PU show a severely impaired performance in a negative geotaxis climbing assay compared to controls.

Aged flies expressing Hsap\YARS^{G41R.Scer\UAS} under the control of Scer\GAL4^Act5C.PU show impairment in flight ability; 45% fail to fly.

Flies expressing two copies of Hsap\YARS^{G41R.Scer\UAS} under the control of Scer\GAL4^nSyb.PS show an impaired performance in a negative geotaxis climbing assay compared to controls.

Flies expressing two copies of Hsap\YARS^{G41R.Scer\UAS} under the control of Scer\GAL4^OK307 show electrophysiological defects in the giant fiber system. Some flies have normal response latencies but defects in following high frequency stimulation, whereas some flies are more severely affected and have an increased response latency. The severity and frequency of the mutant phenotype increases with age. Flies which show electrophysiological defects have morphological defects in the giant fiber synaptic terminal, which is abnormally thin.