Control of hereditary disorders.

Genetics is the study of biological variations, and medical genetics is the study of those variations that result in, or predispose to, disease. Although at first blush these definitions seem straightforward, they are, in fact, quite contrary to the present perceptions of what genetics is all about. To the pediatrician it is about birth defects and syndromes, to the internist it is about arcane metabolic and morphological disorders, and to the US Sur­ geon General it appears to be summed up in his phrase "search and de­ stroy." Screening and antenatal diagnosis of genetic abnormalities are mainly in the province of pediatricians and obstetricians. Patients referred to genetics clinics are usually children with dysmorphic syndromes and developmental abnormalities. This and the likely over-representation of pediatricians among medical geneticists at the medical school may lead to the impression by students and faculty that medical genetics is mainly concerned with developmental defects. This obscures the comprehensive scope of genetics. The genes are a source of differences in structural and metabolic properties that account not only for overt disease but also for predisposition to disease under particular conditions of living. Such observations, as the relationships between human leukocyte antigen (HLA) typing and autoimmune disease, low-density lipoprotein receptor variation and heart attacks, or serum levels of pepsinogen I and peptic ulcer, are a few examples of the many hereditary properties that may be "risk factors" for the diseases of middle and later life (1). The lack of interest among those concerned with preventive medicine is probably related to the preoccupation of medical geneticists with rare con-