Fig. 3. Shh expression is undetectable in ozd limb buds. (A) Normal pattern of Shh expression in a wild-type st. 18 embryo. (B) Comparable stage ozd embryo lacks detectable Shh expression in the limbs (arrows). In situ hybridization to sectioned limb buds confirms this result, showing posterior Shh expression in a wild-type st. 18 wing bud (C) while failing to detect Shh expression in ozd wing buds (D). Normal Shh expression is shown for wild-type st. 19 (E) and 22 (G) embryos, while comparable ozd (F) and (H) embryos exhibit normal domains of Shh expression except in the limb buds (arrow).