ABSTRACT
This chapter presents the developments in the context of experimental designs that may now be performed. Human embryonic stem (ES) cells were isolated from the inner cell mass (ICM) of blastocyst stage embryos. Genetic engineering of human ES cells has also become possible with the development of transfection and infection techniques. Direct injection of DNA into the pronuclei of in vitro fertilized mouse oocytes is a highly efficient method for producing transgenic mice, but the site of DNA integration is random and cannot be preselected. Transfection is the experimental process by which foreign DNA is introduced into cultured cells by physical or biochemical methods. The most popular transfection method for mouse ES cells is electroporation, a process by which application of short electric impulses creates transient small pores in the bilayer membrane, allowing introduction of exogenous DNA into the cell.
