 To do this, they first remove eggs from a female of the recipient species and fertilize them in vitro. Meanwhile, they have cloned the desired gene from the donor organism. They then inject the cloned DNA directly into the nuclei of the fertilized eggs. Some of the cells integrate the foreign DNA, the transgene, into their genomes and are able to express the foreign gene. The engineered embryos are then surgically implanted in a surrogate mother.
