<cell biology> Cells die (nonaccidentally) either when they have completed a fixed number of division cycles (around 60, the Hayflick limit) or at some earlier stage when programmed to do so, as in digit separation in vertebrate limb morphogenesis.

Whether this is due to an accumulation of errors or a programmed limit is unclear, some transformed cells have undoubtedly escaped the limit.

See: apoptosis.

(26 Mar 1998)