Figure 4.

β-Galactosidase assay in embryos after flipping out of the test element. (A) The test element flanked by loxP sites is removed upon crossing the transgenic line to a Cre expressing fly. (B) Boundary activity of mosquito test elements is position independent as the removal of the test element restores the lac-Z staining. Top and bottom row of the lower panel represent the embryos of initial lines and flipped-out lines, respectively. All the genotypes were stained in a grid under identical conditions. (C) Quantitative representation of the relative staining of lacZ in transgenic and flipped-out lines. Embryo images for transgenic initial line and the flipped-out line were processed in ImageJ. P indicates transgenic initial line and ΔP indicates the flipped-out version of the same line. Error bars represent standard deviation from five embryos.