Here is where I think we get into shaky ethical grounds

Genetic Mingling Mixes Human, Animal Cells

"RENO, Nev. - On a farm about six miles outside this gambling town, Jason Chamberlain looks over a flock of about 50 smelly sheep, many of them possessing partially human livers, hearts, brains and other organs.

The University of Nevada-Reno researcher talks matter-of-factly about his plans to euthanize one of the pregnant sheep in a nearby lab. He can't wait to examine the effects of the human cells he had injected into the fetus' brain about two months ago."

..."Stanford law professor Hank Greely, who chaired the ethics committee, said the board was satisfied that the size and shape of the mouse brain would prevent the human cells from creating any traits of humanity. Just in case, Greely said, the committee recommended closely monitoring the mice's behavior and immediately killing any that display human-like behavior." read more...

Imagine if they injected the brain cells of a bunch of Neocons into rats and they started to display human-like traits. We'd have a bunch of belligerent rats running around, invading the cages of fellow lab rats, hoarding all the rat food, and reinforcing their cages to keep out the other lab animals. We would definitely have to kill them all. Otherwise, if they ever got into the wild, they'd spread everywhere and the country would be over-run with a bunch of hateful, angry rats.