Generation of genetically modified mice by random insertion of a transgene can be performed by pronuclear DNA microinjection. This technique is a cost-effective and can be fast alternative for generation of knock down, transgene over expression and reporter lines.
A solution containing the transgene is injected directly into the male pronucleus of fertilized oocystes. The eggs are implanted in the oviduct of pseudopregnant recipient mice. At birth the newborn are tested for the transgene detection. All positive animals (called the founders) will be different in their number of copies and transgenes insertion sites.