9.3 Generation of transgenic animal

Transgenic animals can be generated by following methods:

• •  Retroviral infection of pre- or pro-implantation embryos

•  DNA injection of embryos at pronuclear stage.

•  Microinjection of genetically modified embryonic stem cells into blastocysts.

The transgenic animals are created mostly by a well- known technique where fertilized embryos were microinjected by plasmid DNA containing a fused protein in vitro . A micro needle is used to inject the targeted plasmid DNA into the embryo that leads to integration of foreign DNA into the host genome. The pronuclear embryo containing the foreign DNA is then implanted into the recipient animal (Figure 9.1).

Figure 9.1 Standard transgenic approach: