Point mutation.
Lethal when heterozygous with Df(2L)prd1.7 and viable when heterozygous with Df(2L)Prl. Homozygotes exhibit defects in the formation of the RP2 motoneuron. The failure to produce mature RP2 neurons is attributable, at least in part, to GMC4-2a adopting an aberrant cell identity.