Fig. 5. Mammary placodes are absent in Dkk1-expressing embryos. Scanning electron microscopy of the ventral-lateral surface of induced K5-rtTA, tetO-Dkk1 (B,D) and control single transgenic littermate (A,C) embryos at E11.5. Placode number 3 is visible in the control as a mound of cells protruding above the surface of the embryo (arrows in A,C) and is absent in the induced double-transgenic embryos (B,D). A,B were photographed at 75x magnification and C,D at 200x magnification. Scale bars: 100 µm. lb, limb bud.