The biotech empires of Silicon Valley and Europe

 As biotechnology gains prominence among investors, two hubs have emerged as hotbeds of innovation for the resurgent industry. While the two-square-mile patch of South San Francisco bustles with over 70 biotech firms, including Genentech, Amgen and Exelixis, an equally influential geography has grown along the Lemanic Arc of Switzerland and into the heart of Basel, where pharma giants…