Figure 2.

Tissue distribution of homeobox gene expression through mouse mammary gland development. Selected stages of mammary gland development are depicted with reference to the expression patterns of several homeobox genes as demonstrated by in situ hybridization. Expression at a given stage is shown by a bar above the stage. Bars are pattern coded to represent a unique tissue compartment or epithelial structure. Transition points affected by a given homeobox gene mutation are denoted by a hatched box above the arrow representing the transition.