Fig. 4. Abnormal ductal development of transplanted mutant mammary epithelium. Whole-mount analysis of mammary epithelial transplants (A and C, control epithelium; B and D, mutant epithelium) from virgin females. At higher magnification, more and feather-like irregular side-branches are seen in mutant ductal and terminal structures (arrow in D) while control transplants display smooth ducts and normal terminal end buds (arrow in C). Scale bar: for A and B, 300 µm; for C and D, 200 µm.