How Transgenic animals are made?

To add a gene, called a transgene, to the normal chromosome set of an animal, researchers remove a one-cell embryo (the fertilized oocyte) from the oviduct of a pregnant animal and inject a cloned segment of DNA, including a gene of interest, into the male pronucleus.
The researcher then puts the embryo into the oviduct of a surrogate pregnant female who will carry the transgenic animal to term