Research in the field of molecular biology has progressed at a fascinating rate in recent years. Much of this progress results from the development of new laboratory techniques that allow very precise fractionation and analysis of nucleic acids and proteins, as well as the construction of recom­ binant DNA molecules that can then be cloned and expressed in host cells. Progress has been so rapid that there has been a shortfall in the training of appropriately qualified staff. Many existing laboratory workers require retraining, and many educational institutions have had difficulty incor­ porating the new molecular biology techniques into their teaching programs. Although there are several manuals currently available that describe laboratory techniques in molecular biology, they are principally written for the indivi­ dual research worker and are not intended for use in the design of practical classes for students. The aim of this book is to provide just such a series of pro­ ols forthe teaching of practical molecular biology. The idea arose following the success of several Workshops in Molecular Biology, organized and taught by staff in the Biol­ ogy Department of the Hatfield Polytechnic. Gradually, the prools used in the workshops have been incorporated into the Hatfield undergraduate and postgraduate teaching pro­ grams and have now been collected together to form a book.