Ageing chromosomes

There is reason to believe that Dolly, the cloned sheep, inherited some of the wear and tear suffered by her six-year-old mother's cells. The ends of Dolly's chromosomes are shorter than those of normal sheep of the same age, point out researchers at the Roslin Institute near Edinburgh, Scotland. When a cell divides, the end of its chromosomes, called telomeres, are eroded. Older animals have shorter telomeres, and biologists consider shorter telomeres a hallmark of ageing ( New Scientist , Vol 162, No 2188).