Even Clones Sometimes Age Normally US experiments on mice have shown that cloned animals don't necessarily age faster than normally begotten ones. The geneticists were able to clone two groups of mice over four and six generations without shortening their telomeres.
Telomeres are the ends of chromosomes, which get a bit shorter with every cell division.
In comparisons with regular sheep, Dolly the cloned sheep showed extremely shortened telomeres, leading the researchers to conclude that cloned animals have a shorter life expectancy. The animals cloned in this manner showed no shortening of the chromosomes. However, the rate of cloning success dwindled from each generation to the next. In the first group no more offspring developed from a total of 670 cloned cells in the fifth generation. In the second group, the sixth generation yielded only a single mouse, which was unfortunately eaten up by its mother.