Genetic disorders have emerged as a prominent cause of morbidity and mor tality among infants and adults. As many as 10% to 20% of hospital admis sions and at least 10% of the mortality in this age group are due to inherited diseases. There are at least two factors that have brought genetic disorders into the forefront of pediatrics. One is a great reduction in childhood mortality due to infections and nutritional deficiency states, and the other is the rapid progress made in the identification of genetic defects. Amniocentesis, chorionic villus sampling, and recombinant DNA technology have...