Fig. 4. Activity of Hoxb6-Cre revealed by analysis of Rosa-26 reporter mice. Ages of embryos are as indicated; the number of pairs of somites are: 8 (A), 25 (B,D,F), 20 (C) and 22 (E) pairs of somites. The arrow in A indicates the presumptive hindlimb territory. Arrows in C,D,G indicate anterior areas lacking Cre activity. In E and F the extent of the forelimbs is marked with lines. The arrowheads indicate a boundary between solid blue and diffuse ß-gal staining, indicating that Cre activity gradually extends anteriorly. FL, forelimb; HL, hindlimb.