At top and bottom left are two mice in which a gene named Hoxb1 has been disabled. The gene controls the development of nerves needed for facial expressions. When a puff or air was blown into the face of the first mouse (top right), it was unable to blink its eyes, wiggle its whiskers or pull back its ears due to facial paralysis caused by the lack of the Hoxb1 gene. But in the mouse on the bottom, a key piece of the Hoxb1 gene was inserted into a gene named Hoxa1, in effect recreating an ancient gene that once did the job of both Hoxb1 and Hoxa1. So when a puff of air was blown in the face of that mouse (bottom right), it was able to blink its eyes, wiggle its whiskers and fold back its ears -- thanks to the reconstructed, anicent gene.