Standard molecular biology techniques are used widely in biomedical re­ search and have had a major impact on the understanding of physiologic processes and disease mechanisms. They also play an increasing role in mo­ lecular genetic diagnosis and new therapeutic approaches. This laboratory manual is designed for researchers who need reliable pro­ tocols for their laboratorywork. It provides a step by step approach to stan­ dard methods of molecular biology. A wide range of topics is covered by protocols for immediate application in the laboratory. These include pur­ ification, isolation, labeling, hybridization, sequencing and enzymatic mod­ ification ofDNA or RNA, polymerase chain reaction, cloning, libraries, and protein techniques. The manual is based on experience with a practical course in molecular biologytechniques, which was taught bythe authors. Since most methods in molecular biology recapitulate in a test tube mechanisms that occur natu­ rally in the cell, the first three chapters describe and illustrate basic mechan­ isms of molecular biology. U nderstanding more about these basic mechan­ isms will enable the researcher to apply techniques more specifically, based on the knowledge of their potential and limits. W e hope that users find this manual a helpful guide on their road to exciting insights.