_:b663964004 . _:b663964004 . _:b663964004 . _:b663964004 . _:b663964004 . _:b663964004 . _:b663964004 . _:b663964004 . _:b663964004 "Orthology that involves two genes when duplications more recent than the species split have occurred in one species but not the other." .