The classical model for apoptosis is the worm C. Elegans. This is a simple organism that produces exactly 1090 cells during development, of which exactly 131 undergo apoptosis. Investigation of this worm has demonstrated five families of genes that regulate apoptosis in C. Elegans.

1.       Genes that trigger apoptosis, including the C. Elegans death (ced) gene ced-4.
2.       Genes involved in execution of apoptosis, notably ced-3.
3.       Genes required for the engulfement of the dead cell.
4.       Genes required for disposal of the cellular shroud.
5.       A single gene (ced-9) that suppresses apoptosis.

Worm of Doom. C. Elegans, perhaps the most-studied worm in the world.