U.S. Department of Health and Human Services

Mammalian Developmental Biology Section

Jurrien Dean, M.D., Chief

​Research Images

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Early Mouse DevelopmentMaternal RNA and proteins accumulate during oocyte growth. The zona pellucida that surrounds ovulated eggs (green) is modified following fertilization (red) to prevent polyspermy. Activation of the embryonic genome occurs in the 2-cell embryo and, following the third cell division, embryos compact to form morulae and then blastocysts that implant on the wall of the uterus.Early Mouse DevelopmentEnlarge
Mouse FertilizationFertilization occurs in the ampulla of the oviduct where the fertilizing sperm encounters an ovulated egg. After initial binding to the zona pellucida, the sperm penetrates through the zona matrix to fuse with the egg plasma membrane. The subsequent cortical granule reaction leads to a potent block to polyspermy.Mouse FertilizationEnlarge