Online Magazine The Scientist included a nice piece on telomeres in their May 2012 issue, explaining how they change as we age and contribute to things like cancer.
“The ends of linear chromosomes have attracted serious scientific study—and Nobel Prizes—since the early 20th century. Called telomeres, these ends serve to protect the coding DNA of the genome. When a cell’s telomeres shorten to critical lengths, the cell senesces. Thus, telomeres dictate a cell’s life span—unless something goes wrong. Work over the past several decades has revealed an active, though limited, mechanism for the normal enzymatic repair of telomere loss in certain proliferative cells. Telomere lengthening in cancer cells, however, confers an abnormal proliferative ability.
In addition to cancer, telomeres have been found to be involved in numerous other diseases, including liver dysfunction and aplastic anemia, a condition in which the bone marrow does not produce a sufficient supply of new blood cells. Inadequate telomere repair and accelerated telomere attrition can be molecular causes of these diseases, and targeting these processes may lead to the development of novel therapies…
Telomeres shorten as we age. By analogy to the cellular mitotic clock, telomeres have been postulated as a marker of “genetic age,” and telomere length has been marketed as a simple predictor of longevity. ”