The ato coding sequence present in atoFaFG4 has been removed by FLP-mediated recombination. This allows the GAL4 coding sequence present to be expressed. A single FRT site remains upstream of the GAL4 coding region, and the inverted attR sites found in atoFaFG4 are still present.
In single-cell atoG4 clones, mutant cells never become R8 as expected but differentiate as non-R8 photoreceptor neurons if neighbored by a wild-type R8 and send axons toward the brain.