Inside chromosomes are telomeres that age as we age, and may serve as indicators of how long we'll live.
Wrinkles may betray our age externally, but our cells divulge their age -- and chronicle life's toll -- at the tips of our chromosomes. These tips, called telomeres, may also foretell our risk of early death.
Telomeres are the protective caps made of repetitive chunks of DNA that keep the rest of the gene-laden chromosome from disastrously unraveling. But they lose bits of themselves with each cell division, so over a lifetime, like a counter, telomeres shorten. Eventually, shortened telomeres send cells into senescence, a retirement-like state in which they no longer divide or remain active but do not die.