Embryonic stem cells (ES): These are pleuripotent cells of early embryo (blastocyst) capable of giving rise to all differentiated cells, including germ line cells. Embryonic stem cells (ES) can be cultured maintained and are able to proliferate. The method of producing transgenic mice by genetically modified embryonic stem cells is as follows:

(i)  Embryonic stem cell (ES) culture is initiated.

(ii)  The ES are transformed and screening is done in PCR analysis.

(iii)  Transformed cells can be cultured and inserted into blastocyst, which are then implanted in foster mother.

(iv)  Transgenic lines are determined by crosses from founder mice.