"The Advanced Methods" series is intended for advanced undergraduates, graduate students and established research scientists. Titles in the series are designed to cover current important areas of research in life sciences, and include both theoretical background and detailed protocols. The aim is to give researchers sufficient theory, supported by references, to take the given protocols and adapt them to their particular experimental systems. The recent isolation of human embryonic stem cells and the potential of these cells for therapeutic applications has generated an entirely new methodology. Similarly, gene targeting methodology has recently been extended to nuclear donor cells in ungulate species. This volume will be invaluable for both new and established researchers in the field of human embryonic stem cells, and to biotech companies engaged in the production of transgenic proteins in livestock, xenotransplantation and the development of animal models.