2. Retrovirus- medicated gene transfer

A retrovirus is a virus that carries its genetic material in the form of RNA rather than DNA.

This method involves:
* Retroviruses used as vectors to transfer genetic material into the host cell, resulting in a chimera, an organism consisting of tissues or parts of diverse genetic constitution
* Chimeras are inbred for as many as 20 generations until homozygous transgenic offspring are born.