The subject of Genetics is gaining utmost importance in the medical science. However, most of the medical students find this subject difficult to understand and therefore, neglect it. The aim of this book is to present the text in such a way that it provide the clear and conceptual understanding of the subject. A simple and concise account of the genetic basis of various diseases is given to make the subject directly applicable to the medical science. It is hoped that the undergraduate and postgraduate students of medical science and clinicians will find this book interesting and useful.