Abstract：Efficiency and specificity, are the limiting factors in preparation of transgenic animal. This review describes the recently developed animal gene transfer techniques, including gene transfer into the testis, ovary and RNA interference for improving efficiency of non-site specific methods; gene targeting in embryonic stem cells, somatic cells and primordial germ cells for site specific methods; and site- and time-specific gene targeting and controlled expression of transferred genes. The merits and disadvantages for each method are also discussed, as well as potentials of using these methods to develop transgenic animals.
