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.