Many of the signals required to induce formation of specialized adult cells must be present in these tumors, but unlike embryos, tumors generate adult cell types in a hopelessly undirected manner.
If a developing embryo is not to end up a mass of disorganized tissues, it must do more than generate adult cell types. Embryos must orchestrate and choreograph an elaborate stage production that gives rise to a functional organism. They must direct intricate cell movements that bring together populations of cells only to separate them again, mold and shape organs through the birth of some cells and the death of others, and build ever more elaborate interacting systems while destroying others that serve only transient, embryonic functions. Throughout the ceaseless building, moving, and remodeling of embryonic development, new cells with unique characteristics are constantly being generated and integrated into the overall structure of the developing embryo. Science has only the most rudimentary understanding of the nature of the blueprint that orders embryonic development. Yet, recent research has begun to illuminate both how specific adult cells are made as well as the central role of stem cells in this process.
The term "stem cell" is a general one for any cell that has the ability to divide, generating two progeny (or "daughter cells"), o ...Show more