Development of mrad50 mutant embryos. (a–f) Hematoxylin/eosin staining of sagittal sections of wild-type embryos (a, c, and e) and mutant embryos (b, d, and f) at E6.0 (a and b), E6.5 (c and d), and E7.5 (e and f). Note the smaller size of the mutant embryos. By E6.5, the homozygous mutant embryo has not developed appreciably beyond E6.0 stage. In many cases, the mutant embryo is in the process of being resorbed. By E7.5, the homozygous mutant embryo is completely resorbed. (Bar = 100 μm.) (g–j) BrdUrd labeling of proliferating cells in wild-type (g and i) and mutant (h and j) embryos at E6.0 and E6.5, respectively.