Advances in genetics over the past 50 years have dramatically changed the understanding and management of inherited disorders, and are beginning to have a major impact on the practice of medicine overall. The rapidity of these advances means that clinicians and scientists in the field are often unfamiliar with the key research that has led to many developments that now are accepted and familiar. Few have time to search for the original papers, which are scattered and often difficult to obtain. This collection has been edited mainly for medical geneticists and genetics researchers who wish to learn more about how their field originated and developed. Brief, clearly written commentaries on each paper and section place the work in its current context and serve to unify the different parts of the book. They also help make it a readable and authoritative source of information. The papers chosen fall into several groups. First are classic descriptions of important genetic disorders, often from the pre-mendelian era. The following sections deal with the definition of human mendelian inheritance, the origins of human cytogenetics, the early development of the human gene map and the transition from biochemical genetics to human molecular genetics, the relatively recent studies that have shown how mendelian principles are increasingly modifiable, and finally advances in the treatment and management of genetic disorders, which are placed in their social context.