A process in which a person's or an embryo's DNA is isolated and tested for the presence of specific genes or defects that could indicate the future onset of some disease. if (window.googletag) {googletag.cmd.push(function() { googletag.display('dcomMobileSERPDisplayTopAd-300x250'); });} else {console.error('googletag not defined, dcomMobileSERPDisplayTopAd-300x250');}