A regulated form of cell death. Measuring it helps distinguish failed cell specification from selective loss of an already specified biological population.
Typical execution includes protease activation, chromatin changes and packaging of cellular material for removal. Clearance by other cells can limit leakage of intracellular contents. The process is therefore more specific than any observation of reduced cell number or a cell failing to divide. [ref]
Molecular Biology of the Cell, 4th edition by Bruce Alberts and others. Chapter 17, Programmed Cell Death
A BCL-2-family effector promoting mitochondrial outer-membrane permeabilization during apoptosis. Its activation differs from merely increasing expression of an apoptotic gene.
Articles by others on the same topic
Power, Sex, Suicide by Nick Lane (2006) part 5 "Murder or suicide" mentions that apoptosis has two main functions:
- prevent cancer
- but it is also an important part of body development, e.g. fingers are separated because cells between them kill themselves. Otherwise we would have webbed feet like ducks. There is also a lot of apoptosis during the development of the brain. This has been observed notably in C. elegans see also: Section "C. elegans cell lineage".