A human DNA gene for making the blood protein antithrombin was introduced into a goat shown in the photo. Antithrombin is an enzyme that inhibits blood clotting. The goat can secrete milk that contains the protein which can help patients suffering from a rare hereditary disorder that causes thrombophilia, a high tendency to form blood clot in the blood vessels.
Urry, Lisa A.. Campbell Biology (p. 434). Pearson Education. Kindle Edition.