When Dolly, the first mammal cloned from an adult cell, was born, many researchers wondered what the effects of starting life with 'old' cells might be. The scientists who cloned Dolly now report that the famous sheep's DNA might be showing its age.
Telomeres are segments of DNA found at the tip of each chromosome in nonbacterial cells.
Replication of telomeres is regulated by a special enzyme called telomerase. As organisms age, the telomeres tend to shrink in size. Dolly was cloned from cells derived from the udder of a six-year old Finn Dorset ewe. The researchers used restriction enzymes to measure the mean sizes of terminal telomere fragments for all of the animals in the study. The results from the control sheep confirmed that the telomeres do indeed decrease in size with age.