The stable introduction of recombinant DNA into the germline of mammals is one of the major technological advances in biology and has greatly facilitated the study of gene function in development and disease,as well as the development of biotherapeutics. Landmark experiments conducted in the early 1980s established the feasibility and reproducibility of stably introducing DNA by microinjection into the male pronucleus of single-cell mouse embryos (1 –5 ).The utilization of transgenic mice now represents a major strategy for the examination of genetic and biologic questions in vivo,both in basic research and industry.
