New Scientist: Chromosomes aged 10 years by stress
Psychological stress may be enough to age a woman’s chromosomes by 10 years, a new study suggests.

A piece of DNA called a telomere caps the ends of each chromosome, protecting those ends and promoting genetic stability. Each time a cell divides, the telomeres shorten so that daughter cells have slightly shorter telomeres than their parents.

But in young people, an enzyme called telomerase corrects the process, regenerating the ends. However, in older people the telomeres shorten significantly and eventually their replication stops altogether.