This book offers an up-to-date treatment of the molecular genetics of both eukaryotes and prokaryotes, along with related cell and molecular biology. The revisions reflect the explosion of new information, greater coverage of developmental biology, and an expansion of introductory and explanatory material. It approaches the study of genetics from the perspective of the gene and addresses the questions of what a gene is, how it reproduces, how it is expressed, and what controls its expression. Also explained is how a gene is represented in protein, and works backward at the molecular level to the DNA itself. The biochemical basis for heredity, transcription and its regulation, processing RNA in eukaryotes and development during embryogensis are topics also discussed in the book.