Summary

As an embryo develops from a small cluster of stem cells, those once "blank slate" cells begin to take on more specialized roles like brain, liver or muscle cells and organize themselves into three-dimensional structures such as tissues and organs. The fate of each cell—what type of specialized cell it will become—depends on which genes are turned on or off in the cell. These patterns of gene activity shape the cell's structure and function, enabling it to take on a specific role in the body.

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