Fig. 4. Transgenic embryos do not develop a functional cloaca. (A) Overview of the rhodamine gut injection assay used to assess cloacal function in wild-type and transgenic embryos. (B,C) Injected wild-type embryos secrete the rhodamine dextran from their cloaca within minutes. (D,E) Transgenic embryos develop a buildup of rhodamine dextran at the end of their gut, and they do not excrete the dye into the media. B,D are brightfield views; C,E are brightfield/fluorescent merged images. Brackets in B-E indicate the gut terminus.