Gene mutations can pass silently for generations until two carriers mate; then children have a one-in-four chance of getting the disease.
Some of mankind’s most devastating inherited diseases appear to be declining, and a few have nearly disappeared, because more people are using genetic testing to decide whether to have children.
Births of babies with cystic fibrosis, Tay-Sachs and other less familiar disorders have dropped since testing came into wider use, The Associated Press found from a review of studies and interviews with numerous geneticists and other experts.
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