Immortal Cells

The clusters of human skin cells basking in a sterile incubator, with alarms poised to go off if the level of carbon dioxide drops or the temperature wavers from 98.6 degrees, appear to be blessed with eternal youth. Under normal circumstances, skin cells divide about 50 to 70 times and then quickly wither and stop dividing. But after nearly two years in a laboratory at Geron, a Menlo Park, California, biotech company, these genetically altered cells are approaching 400 divisions and still show no signs of aging. They just keep multiplying.