Homozygous and jumuL40/Df(3R)B22-5 embryos show duplication of the RP2 neuron (expressivity of the phenotype is 15% and 27% respectively). jumuL40/Df(3R)B22-5 embryos show greater than 95% penetrance of the RP2 neuron duplication phenotype. The extra RP2 neuron appears to be derived from the RP2sib cell. The GMC4-2a cell appears to retain a wild-type identity in these embryos.