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Unformatted text preview: 548 Chapter 17 Genetic Regulation of Cell Number: Normal and Cancer Cells itself senses damage and initiates its own death. In other cases, the cell-death program is initiated by signals from neighboring cells that tell the cell to die. These signals are in the form of proteins or other molecules that attach to receptors on the surface of the stem cell or the dying cell. Eukaryotic cells have elaborate intercellular signaling pathways as status indicators of the environment. Some signals, called mitogens, stimulate proliferation, whereas others inhibit it. Death signals can activate apoptosis, whereas survival signals block activation. The cell-proliferation and cell-death machinery must be wired into the cellular systems that are survey- ing the cells external environment for the presence of signaling molecules. Thus intercellular signaling path- ways typically consist of several components: the signals themselves, the receptors that receive the signals, and the transduction systems that relay the signal to various...
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This note was uploaded on 01/10/2011 for the course BIOL BIOL taught by Professor Johnson during the Spring '08 term at Aberystwyth University.
- Spring '08