Nobel Prize for Telomeres Three Americans will receive the Nobel Prize in Medicine this year for their research in figuring out how telomeres work (see article in the New York Times). Telomeres are the ends of DNA strands that keep the DNA from being shortened (and damaged) when cells divide. Telomeres have a major role in aging, because when the telomeres are "used up" the cell can no longer replicate successfully.
Even more interesting, was the discovery of telomerase, an enzyme that protects telomeres during cell replication. When telomerase is switched "on" the cell becomes immortal - it is able to replicate endlessly without dying. This happens in fetuses and kids (until the age 4 or 5) and then it is switched off. Telomerase also is switched "on" in cancer cells, allowing them to replicate widely without dying.