Ageing is all in our genes. The key is a thing called telomere, a tiny bit of ilfe's software at the tip of every chromosome. It is a biological clock, ticking inside each of your cells and telling them when to call it quits. The telomere, containing bits of DNA, is shortened each time a cell divides. Telomerase is an enzyme that repairs damaged telomeres.
Most human cells stop making telomerase early in life.
Dolly and two other sheep cloned by nuclear transfer exhibit shorter telomeres than age-matched control sheep. Dolly, which was cloned from a mammary cell from a six-year old adult sheep, showed telomere loss of approximately 20 percent. Hence, in cloning, especially in genetic engineering of cloned cells or animals, cellular senescence limits the efficiency and potential of the technology. Telomere lengthening has the potential to delay cellular ageing and thereby extend the duration of cell-based experiments and improve the efficiency of genetic engineering.