The fetal fibroblasts used to clone the other animal had spent only a minimal time in culture. It is likely that these differences in telomere length can be explained on the basis of the different ages of the cells used to clone the different animals, he noted. However, the sample size was small and the possibility that these differences reflect only normal variations in telomere length cannot be excluded. The researchers don't know whether or not the telomere changes reflect changes in the physiological ages of the animals. It may be that the effect on telomeres may have no effect on the longevity of cloned animals.
Veterinary examinations indicate the animals are happy and healthy.
Dolly herself has produced two litters of lambs. Other researchers have cloned mice from mice clones and report no apparent effects on longevity in those animals. Telomeres are believed to act as a protective cap on on chromosomes. With each round of DNA replication that occurs when a cell divides, a little bit of the telomere wears away. Current research suggests that once a cell has replicated a certain number of times, the telomere degrades to such a point that the cell commits suicide.