Fig. (1) The scheme for the screen. Two days old Canton S wild type males were starved for 12 hrs and then fed with vitamin C and ZnCl₂ in 1% sucrose solution for 12 hrs. These flies were allowed to recover for ~4 hrs and then mated with attached XX virgin females en masse for 2 days, transferred to new bottles and allowed to lay eggs for another two days before discarding. The male progeny were then examined for any mutations in the eye-color gene white . A loss of function mutation in this gene should give male progeny that have white eyes or mosaic patches of white pigments in the eye.