Generation of new mouse lines through BAC transgenesis or TALEN-mediated transgene insertion. (a) In consequence of the random integration of the vector during the construction of BAC transgenic mice the founders need to be screened for the appropriate expression pattern. (b) In contrast, TALEN-constructed transgenic mice only need to be checked by molecular biology methods for presence of the appropriate knock-in event. As a side product, knock-out alleles are usually generated as well.