Mouse Embryo Developing in a Culture Dish (VIDEO) University of Pittsburgh This video is under embargo. Please login to access this video. To view this video please enable JavaScript, and consider upgrading to a web browser that supports HTML5 video Caption After fertilization, cells within a newly-formed mouse embryo divide and multiply. The cells all have the same DNA, but gene expression patterns diverge as they start to take on different roles. Once there are a few dozen cells, a fluid-filled cavity appears in the center of the embryo. Cells on the surface will become the placenta and the clump of cells nestled to one side will become the fetus. With epigenetic disorders, the gene expression instructions aren't passed down or maintained properly. In Beckwith-Wiedemann syndrome, for example, the loss of epigenetic marks causes an overgrowth of the placenta and certain parts of the fetus. Credit Audrey Kindsfather Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.