Molecular genetics. Therapy or terror?

In the past three decades, the application of information derived from cardiovascular research markedly reduced the death rate from ischemic heart disease, the number one killer in the Western world. This resulted, in part, from the integration and focusing of innovative techniques developed and employed by well trained investigators enticed from multiple scientific and clinical disciplines. Throughout this interval, it was perhaps appropriate on the basis of priority that another group of cardiac diseases referred to as cardiomyopathies received very little attention. A second, perhaps more legitimate, reason for this lack of attention is that many of these diseases, at least in this country, are inherited and until recently, techniques were not available to identify the underlying genetic defect. The introduction of recombinant DNA techniques in the 1970s followed by their application in molecular genetics drastically changed the potential to explore the molecular basis of these disorders. Previously, unless one knew the protein defect responsible for the inherited disorder, it was almost impossible to identify the gene. The development of linkage analysis makes it possible to map the chromosomal locus of a disease related gene without knowing the responsible protein and, once mapped, another technique referred to as positional cloning makes it possible to identify the responsible gene. Chromosomal mapping of a disease locus through linkage analysis consists of showing one or more DNA markers of known chromosomal location