Last year, the scientists who created Dolly the cloned sheep raised the concern that she was aging prematurely. Their fear was prompted by the finding that protective tips on her chromosomes seemed shorter than normal for a lamb her age. A new study of cloned cows counters that disquieting finding, however. It even suggests that cloning can create cells, and perhaps animals, that thrive longer than normal.
In the April 28 Science, Robert P. Lanza of Advanced Cell Technology in Worcester, Mass., and his colleagues report that they've cloned cows from aged cells. They find that cells from the clones have longer DNA tips, or telomeres, than the original cells and show other signs of youthfulness.
One telomere researcher says that the new data should dispel concerns that clones will die earlier than normal. "It provides great reassurance," says Robert A. Weinberg of the Massachusetts Institute of Technology.
Lanza suggests that his group's use of cells that h