Should the findings be verified, they could affect this area of research, scientists said. Drawing any clear implications for the future of human cloning is much too premature, the scientists said. A telomere is a region at the end of a chromosome, which carries genetic information. In most cells, this cap that protects the chromosome ends from fraying progressively erodes as the animal ages. Experiments in mice in which telomerase was knocked out have shown that excessive shortening of the telomeres can lead to reproductive and other problems in four to five generations.
Experiments also show shorter telomeres in sheep cloned from embryonic and fetal cells.
These pieces of DNA and and the enzyme telomerase have long fascinated researchers because of their apparent role in the aging process. Studies indicate they act as a sort of cellular fuse, bearing the brunt of chromosomal erosion that results from the DNA replication that occurs when a cell divides. Eventually, it is thought, when telomerase ceases to maintain a cell's telomeres efficiently, the caps are worn away, and the cell commits suicide. The finding comes at a time of increasing cloning activity. Since Dolly's arrival in the Scottish laboratory barnyard, scientists have cloned a number of livestock and laboratory animals - some aimed at producing more reliable food products, some intended to serve such research purposes as the production of pharmaceuticals.