Representative expression analyses of Col2a1 (A–C), Sox9 (D–F), Col10a1 (G–I), Ihh (J–L), Ptch1 (M–O), and Fgfr3 (P–R) transcripts in 18.5 dpc tibia sections from wild-type, mutant, and rescue embryos. The panels demonstrating Ihh data contain insets that enlarge the prehypertrophic/hypertrophic zone of expression. Results were observed consistently in five independent experiments with at least four embryos for each mRNA probed. In situ hybridizations with DIG-labeled RNA probes were performed on 40 µm sections; cartilage elements are outlined for clarity.