This book describes the structures of genes in molecular terms and summarises knowledge about bow their activity is regulated. The methodology of genetic engineering for the production of useful medical and other products in bacteria is presented. A number of specific examples are discussed in detail, taken from bacteria (which are most clearly understood) and higher organisms, including humans. There is dicussion of some diseases which have a genetic origin, such as thalassaernia and sickle cell anaernia. Recent research which is linking the genesis of cancer to a family of viruses is described. Designed as a text book for honours students in the fields of genetics, biochemistry and microbiology, the approach in this book is mainly biochem...