Frontal views on whole mount in situ hybridization analysis of control (A-D), Prx1+/-;Prx2-/- (E-H) and Prx1;Prx2 double mutant (I-L) embryos at E11.5. A, E, I show that the expression of dHand in the medial region of the mandibular processes is similar in all three genotypes. eHand is expressed in a restricted domain in the midline of the mandibular processes in the control (B). Note the reduced domain of expression of eHand in Prx1+/-;Prx2-/- (F) and the absence of expression of eHand in the Prx1;Prx2 double mutant (J). C, G, K show that the expression of Msx1 in the mandibular processes of the Prx1+/-;Prx2-/- (G) and Prx1;Prx2 double mutant (K) is extended into the aboral side in the midline region as compared to control (C). D, H, L show that the expression of Msx2 in the mandibular processes is similar in all three genotypes. Scale bars =1 mm.