Figure 2.

Skeletal defects in p21^−/− p57^−m/+ mutants. (A–C) p21^−/− p57^−m/+ embryos display altered posture. (D,E) Skeletons of E18.5 embryos stained with alcian blue to identify cartilage and alizarin red to identify ossified bone. (F) Bifurcation of the ninth rib (arrow) is observed in p21−/− p57^−m/+ embryos. (G) The femur of E18.5 embryos. The arrow indicates cartilage outgrowth. (H–J) Sternia and ribs of E18.5 embryos. Only 7 of the 13 ribs attach to the sternum. Note a bifurcation in the seventh rib in the double mutant (arrow in J). Embryos in G–J stained as in D and E.