However, unlike the differences in the pattern of degeneration between vertebrate rods and cones, the asymmetric retinal degeneration GMR-DHDDS-RNAi flies is not due to differential expression of photopigments, as R1-6 cells express Rh1 rhodopsin, and these cells do not express any other photopigments. The gene discussed is RHO; the disease is retinal degeneration.