Abstract
Recent advances in biotechnologies have made it possible to manipulate mammalian embryos. This technology in combination with the recombinant DNA technology provides embryos with new and purpose oriented genetic information. Subsequent embryo transfer to the pseudopregnant females also makes these manipulated embryos develop to term as transgenic animals. Transgenes integrated in the transgenic animals are usually transmitted to their off-spring according to the Mendel's Law. Therefore, once we obtained a particular transgenic animal, we could rear them as a strain non-existent in nature. In this report, methods of producing transgenic mouse and a few examples which were applied to the analyses of biological functions are mentioned .