Scientists in Japan has received government permission to grow human organs in animals for the first study of its kind in the country.
The research involves genetically modifying sheep or pig embryos so they cannot grow a specific organ.Human induced pluripotent stem(iPS) cells are then injected into the embryo in the hope that the DNA will fill in the missing code.
The hybrid embryos would then be implanted back into the original animal or a surrogate and the baby animal would be born with a human organ.
This is the first step towards a future where human organs for transplant could be grown inside animals.
However,critics have argued that the human cells could stray beyond the targeted organs into other areas of the animal effectively creating a creature that is part animal,part person.
Further,many animals such as pigs have a shorter lifespan than humans, meaning that their tissues age at a quicker rate.Disease transmission and permanent alteration to the genetic code of animals are also causes for concern.