New advances in animal transgenic technology.

The technique of pronuclear microinjection is the most reliable and popular method for transgenic livestock production to date. However, pronuclear microinjection has been proven to be inefficient in producing transgenics and in inserting a piece of DNA into a specific site in the host genome. In the past 20 years, some new approaches have been used. These include sperm-mediated DNA transfer, retroviral mediated DNA transfer into oocytes, somatic cell carrying exogenous genes nuclear transfer, the use of embryonic stun (ES) cell. But these ways can not solve existing problems thoroughly. In recent papers, the existing techniques have been improved and significant progress has been made in developing transgenic techniques.