The Battle Against Aging/Counting the Lives of a Cell; The Quest to Beat Aging; Scientific American Presents; by Evelyn Strauss; 6 Page(s)

Biologists have always warmed to the notion of a cellular alarm clock that would mark off the moments of a cell's life and ring when its time to die had arrived. The existence of such a molecular timepiece might suggest ways to slow the ticking or even rewind the clock and thus give people lengthened, healthier lives.

Would that biology were so manifestly simple. Mother Nature doesn't wear a Rolex, and scientists have yet to hear a ticking sound inside a cell's walls. The closest thing that anyone has found to a cellular clock resides at the tips of chromosomes in the nucleus of cells. Chromosome ends, stretches of DNA called telomeres, do not contain genes that program hereditary traits. But they do bear some resemblance to a kind of clock or a fuse that sets off a time bomb.