Males can have a shorter lifespan than females due to repetitive sections of the Y chromosome that create toxic effects as males age. These new findings appear in a study by Doris Bachtrog of the University of California at Berkeley published on April 22 in PLOS Genetics.
In humans and other species with XY sex chromosomes, females often live longer than males. One possible explanation for this disparity may be repetitive sequences in the genome. While both men and women carry these repeats, scientists have suspected that the large number of repeats on the Y chromosome can create a “toxic y effect” that shortens men’s lives. To test this idea, Bachtrog studied male fruit flies of the Drosophila miranda species, which have about twice as much repetitive DNA as females and a shorter lifespan. They showed that when DNA is in its tight form inside the cells of young male flies, the repeat sections are deactivated. But as flies age, DNA takes on a looser form that can activate repeat sections, resulting in toxic side effects.
The new study shows that repeat-rich Y chromosomes are a genomic handicap for males. The findings also support a more general link between DNA repetition and aging, which is currently poorly understood. Previous studies of fruit flies have shown that when repeated cuts become active, they impair memory, shorten lifespan, and damage DNA. This damage likely contributes to the physiological effects of aging, but more research is needed to uncover the mechanisms underlying the toxic effects of repeated DNA.
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