Cell death is under genetic control, and requires “executioner” genes that encode enzymes called caspases. During development, the absence of neurotrophic signaling eventually switches these cell death genes on. Once the cellular suicide program has been activated, the caspase proteins begin to break the cell down from within: the cell’s DNA and scaffold proteins are cut into fragments, causing chromosome condensation, cell shrinkage, and membrane blebbing, all of which give the dying cell a characteristic appearance. Finally, immune cells called macrophages engulf and clear away the cellular
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