Researchers from Scotland's Roslin Institute and PPL Therapeutics have attempted to answer that question by measuring key pieces of Dolly's DNA called telomeres. All chromosomes are capped with telomeres, tiny strands of DNA that scientists believe hold the key to aging.
Telomeres shorten each time a cell divides, and continuously erode as an animal ages.
The findings will be published in Thursday's issue of the science journal Nature. In 1996, Dolly became the first large animal cloned from genetic material taken from an adult egg. Dolly's shortened telomeres had been predicted as one outcome of cloning, but researches are unsure if such evidence will cause her to die prematurely. Sheep have a life expectancy of 13 years. Genetic tests on Bonnie reveal normal telomeres.