Fig. 6. The A11^13hd allele antagonizes A11 and D11 function in forelimb development. (A) In A11^13hd/13hd D11^+/+ mice, the zeugopod region was shortened to near half of normal length, resembling A11^-/- D11^+/- mice. R, radius; U, ulna. A central bulge was observed in the shortened radii of A11^13hd/13hd D11^+/+ and A11^-/- D11^-/- mice (arrowheads). The olecranon of the ulna, however, was truncated and replaced with a floating sesamoid bone in A11^-/- D11^-/- mice and was more wild type in appearance in A11^13hd/- D11^-/- mice (arrows). (B) Wrist region. The styloid apophyses of A11^13hd/13hd D11^+/+ mice were reduced and/or fused with the ulna and radius, while they were only very mildly affected in A11^-/- D11^+/+ mutants (thin arrows). The styloid apophyses were also reduced and/or fused in A11^-/- D11^-/- and A11^13hd/- D11^-/- mutants (thick arrows).