U.S., Korean scientists clone 'knock-out' pigs

WASHINGTON, United States - An undated photograph released Jan. 3 by the University of Missouri-Columbia shows four ''knock-out'' pigs cloned by a team of U.S. and South Korean scientists in what is thought to be a major step toward producing animal organs for use in human transplants. A so-called knock-out pig has the alpha 1.3 galactosyl transferase gene, that leads to the human immune system rejecting animal organs, inactivated.