Fig. 5. Shh and Ptch expression. Whole-mount in situ hybridization of sonic hedgehog (Shh) and patched 1 (Ptch) expression in embryos (A-C,J-L) or left forelimbs (D-I,M-R) from wild-type, wild-type/raz and raz/raz embryos at different developmental stages. The left forelimbs (D-I,M-R) are viewed from the dorsal surface so that anterior is towards the top. Note the absence of Shh expression in raz/raz limbs (compare D with F and G with I), but the presence of normal expression throughout the remainder the raz/raz embryo (compare A with C). Ptch expression is also absent in the raz/raz limb bud (compare M with O and P with R), but is present throughout the remainder of the raz/raz embryo (compare J to L).