Our genes are made of DNA and exist in long chains called chromosomes. Chromosomes have structures on their ends that are called telomeres, which act as mooring spots at which the proteins and RNA that actually copy DNA attach. Cells possessing the enzyme telomerase are able to lengthen their telomeres, permitting unending cell division and granting effective immortality.
Telomere shortening is believed to play a role in aging.
When our cells have lost the critical length of their telomeres and can no longer reproduce, they move into a senescent phase. Telomeres have been studied extensively in animals and much of what has been learned is applicable to human biology. For additional information about telomeres, see the Telomeres Information Center . Scientists have mapped the nucleic acids that make up telomeres in roundworms. Understanding the structure of the telomere permits a greater understanding of its function.