Figure 6.

 Homeotic transformations in posterior direction in the Y766F mutants. Cervical (A–C) and lumbrosacral (D–F) vertebrae of newborn wild-type (A,D) and Y766Fl homozygous mice (B,C,E,F) are shown. In the Y766F mutants the cervical vertebra C7 often has ribs fusing to ribs on the T1 (B) or to the sternum (C). Other transformations include shift of anterior trabeculi from the C6 to the C5 (arrow in C). At the thoracolumbar level, the T13 often loses its ribs taking a L1 phenotype (E,F, arrow in E points to a remaining distal part of a rib). L6 is frequently fused to the iliac bones (arrow in E), although this phenotype is sometimes seen also in wild-type mice. In Y766F mutants these transformations can occur also over two segments (arrows in F).