During the course the possibilities and difficulties with advanced genetic constructs are covered. Knowledge regarding normal gene regulatory control mechanisms that determine expression over time and place (eg organ) in model organisms such as worms, flies and mice as well as in humans is fundamental to this subject area. Studies of such mechanisms give comprehension of the more frequently employed genetic motifs used in constructs aimed for transgenic experiments. Also molecular genetic methods as well as experimental strategies to determine normal gene function in complex organisms, as well as dysfunction of disease gene variants, are highlighted.