Here is a good example.
Well, once again, the picture is more complicated than that. An international team has just reported in the journal Cell 07/25/2003 that Telomerase Maintains Telomere Structure in Normal Human Cells. They found that all cells express this repair enzyme, and that there is a complicated interplay between regulatory factors to keep a normal cell functioning through multiple cell divisions, with just the right number of telomeres for its needs and environment. Their observations support the view that telomerase and telomere structure are dynamically regulated in normal human cells, and that telomere length alone is not a sign of old age and impending death.
Only when things go wrong with these regulatory mechanisms do cells either lose their last telomeres and die, or go wild into immortal replication cycles as in cancer. Telomerase is a key ingredient both in the regulation of cell proliferation and replicative lifespan, they found. Targeting telomerase in cancer treatment as a bad molecule may not be wise, therefore. Its apparently a vital part of a normal cells operation. One thing is clear: the relationships among telomere length, telomere expression, and replicative lifespan are more complex than previously believed.
The complexity of life and the credibility of Darwinian evolution are inversely proportional. The complexity of life is increasing.