The process of genetic counselling involves many key components, such as taking a family genetic history, making a diagnosis, and providing communication and support to the family. Among these core processes is the mathematical calculation of the actual risk of a possible genetic disorder. For most physicians and counsellors, the mathematics and statistics involved can be a major challenge which is not always helped by complex computer programs or lengthy papers full of elaborate formulae. In this clear, reader-friendly guide, Ian Young addresses this problem and demonstrates how risk can be estimated for inherited disorders using a basic knowledge of the laws of probability and their application to clinical problems. The text employs a wealth of clearly explained examples and "key points" in order to guide the reader to an accurate assessment of the risk of genetic disease. It primarily will appeal to genetic counsellors, geneticists, and all those involved in providing medical genetic services. In this new edition, Dr. Young has pruned redundancies and extensively updated the concepts in each of the 10 chapters, and he has included more working examples, a popular feature of the book.