Fig. 8 . Hox paralog group three gene expression is altered in Cdx1, but not RARE, null mutants. (A,D,G) Wild-type, (B,E,H) Rare^-/- and (C,F,I) Cdx1^-/- specimens were assessed for expression of Hoxa3 (A-C), Hoxb3 (D-F) or Hoxd3 (G-I) by whole-mount in situ hybridization analysis. Somite number is indicated by numbering in each panel, starting with the anterior-most limit of expression of each Hox gene. All three Hox genes were posteriorized by one somite in the Cdx1^-/- mutants (C,F,I) but were unaffected in RARE-null samples (B,E,H).