An immediate consequence of researchers' opening of the genetic book of life has been the opportunity to know about the human genetic makeup and, increasingly, the human genetic destiny. The use of genetic information to predict future onset of disease in an asymptomatic (presymptomatic) person is called predictive genetic testing.

Every aspect of our being is influenced by both genes and environment. In the future, a strategy for influencing development may be to alter genes. At present, the environment in which genes act can sometimes be changed, and thereby moderate their impact (taking medications or avoiding specific hazards, for example). Sometimes there is no known way to change the deterministic power of a gene, though with increased knowledge of its workings there is always hope for future interventions. Whether or not the course of a disease can be altered, predictive information is increasingly available...