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TUESDAY, Aug. 26, 2003 (HealthDayNews) -- Women aren't the only ones who have to pay attention to their biological clock.
Older men's sperm is more likely to contain disease-causing genetic mutations that also seem to increase the sperm's chances of fertilizing an egg, says a study by researchers at Johns Hopkins Medical Institutions.
The researchers made the discovery while they were investigating why a rare genetic disease, Apert syndrome, is more common in children born to older fathers. Children born with Apert syndrome have webbed fingers and early fusion of the skull bones, which has to be surgically corrected.
The Johns Hopkins scientists found that mutation rates in sperm increased as men grew older. But these mutation rates weren't enough to fully account for the increased incidence of Apert syndrome in children born to older fathers.
That led the scientists to suspect that the disease-causing mutations in the sperm also offer some benefit to the sperm.
"For some reason, a sperm with one of these mutations is more likely to be used to make a baby than normal sperm," researcher Dr. Ethylin Jabs, director of the Center for Craniofacial Development and Disorders at Johns Hopkins, says in a news release.
This combination of increased mutation rate and the fertilization advantage offered by the mutations may explain the nearly two dozen other genetic conditions associated with older fathers.
The study appears in the online section of the American Journal of Human Genetics.
Here's where you can learn more about birth defects.