Telomeres are thought to be one of the causes of aging. As the chromosomes undergo replication during mitosis, the end replication problem causes a shortening of the chromosome in somatic cells. Eventually, the shortening of the chromosomes cuts beyond the TTAGGG repeated segments created by telomerases in germ cells, cuting into the coding segments of the genome.
Thus, Dolly, the cloned sheep, is expected to have a shortened lifespan, equivalent to that of the remaining expected lifespan of the original maternal sheep.