The fourth edition of this classical reference book can once again be relied upon to present a cohesive and up-to-date exposition of all aspects of human and medical genetics. Human genetics has become one of the main basic sciences in medicine, and molecular genetics is increasingly becoming a major part of this field. This new edition integrates a wealth of new information - mainly describing the influence of the "molecular revolution" - including the principles of epigenetic processes which together create the phenotype of a human being. Other revisions are an improved layout, sub-division into a larger number of chapters, as well as two-colour print throughout for ease of reference, and many of the figures are now in full colour. For graduates and those already working in medical genetics.