Emery and Rimoin's Principles and Practice of Medical Genetics (eBook)

1.1 Preface (Peter Harper)

Victor McKusick’s chapter “History of Medical Genetics,” which first appeared in the third edition of this textbook in 1996, has provided readers with a masterly account of the origins and development of the field, containing a remarkable amount of information in the limited space available. This has been a historical account as seen by somebody who has lived through most of it, and who has perhaps shaped the development of medical genetics more than any other individual. While this may at times have given a personal slant to the areas emphasized, it provides an unrivaled perspective on the field—indeed for many years it has been the only substantive account, no detailed history of medical genetics having appeared until recently (Harper, 2008).

McKusick’s death in 2008 has sadly removed the possibility of him providing a revised edition of his chapter, but his continued active attention to, and involvement in, the detailed evolution of medical genetics, up to the very end of his life, seen particularly in his interest in the Human Genome Project (HGP) and in the updating of his catalog OMIM, not to mention his many unique photographs, means that the chapter is still of the greatest value, and that it would be wrong, as well as regrettable, were it to be discarded. At the same time though, the highly condensed nature of the text makes it difficult, if not impossible to edit without making radical changes.

Thus, for the present edition of this book, a compromise has been reached, whereby the chapter remains essentially intact, but is framed by this introduction and by a postscript outlining some of the relevant topics that the original chapter does not cover. The web-based format of this new edition will allow the chapter to evolve progressively over the coming years, in keeping with changes in the field, which have not only seen continuing new advances, but have also shown the urgent need for the history of its recent past to be recorded and preserved.

1.2 Introduction

Medical genetics is the science of human biologic variation as it relates to health and disease. Clinical genetics is that part of medical genetics concerned with the health of individual humans and their families. Alternatively, clinical genetics can be defined as the science and practice of diagnosis, prevention, and management of genetic disorders.

Within recent years, medical genetics has become established as a clinical specialty, as the culmination of developments that began in 1956 with the description of the correct chromosome number of the human. With the discovery of specific microscopically visible chromosomal changes associated with clinical disorders, beginning with Down syndrome in January 1959, medical genetics acquired an anatomic base. Medical geneticists now had their specific organ—the genome—just as cardiologists had the heart and neurologists had the nervous system.

The anatomic base of medical genetics was greatly extended with the mapping of genes to chromosomes and specific chromosomal regions, at an ever-accelerating pace, during the past 30 years. Gene mapping has not only enlarged the base for medical genetics but, indeed, as pointed out to me by Charles Scriver (personal communication, 1980), has also provided a neo-Vesalian basis for all of medicine (1). Medical historians tell us that the anatomy of Vesalius published in 1543 was of pivotal importance in the development of modern medicine. It was the basis of the physiology of William Harvey (1628) and the morbid anatomy of Morgagni (1761). Similarly, human gene mapping constitutes an approach to the study of abnormal gene function in all diseases; the gene mapping approach has been adopted by researchers in almost all branches of medicine in the study of their most puzzling disorders. Through mapping, they have sought the basic defect in these disorders, and their clinical colleagues have used mapping information for diagnosis and carrier detection. The ultimate anatomic basis for medical genetics, the DNA sequence, is provided by the HGP.

In this brief history of medical genetics, I trace the foundations of the field that were laid between 1865, when Mendel published his work, and 1956, when the correct chromosome number was reported. I then discuss the events of the past 50 years that have seen the main evolution of the discipline. Finally, I attempt some projections for the future.

1.3 Foundations of Medical Genetics Before 1956

Medical genetics in many developed countries is now a recognized specialty. In the United States, for example, the American Board of Medical Genetics certifies practitioners in the field, including PhD medical geneticists; in 1991, the American Board of Medical Genetics became the 24th organization to join the family of certifying American specialty boards. Medical genetics is a rather unusual branch of clinical medicine; indeed, it may be nearly unique in that it originated out of a basic science. Most specialties started as crafts (or out of a technological advance such as radiography) and only subsequently acquired basic science foundations.

The basic science that developed before 1956 and served as the foundation for the developments of the past 50 years included Mendelism, cytogenetics, biochemical genetics, immunogenetics, and statistical, formal, and population genetics.