Centrum Wiskunde & Informatica (CWI), Life Sciences Group, Science Park 123, Amsterdam 1098 XG, The Netherlands and Department of Computer Science and Brown University, Providence, Rhode Island 02906, USA.|Centrum Wiskunde & Informatica (CWI), Life Sciences Group, Science Park 123, Amsterdam 1098 XG, The Netherlands and Department of Computer Science and Brown University, Providence, Rhode Island 02906, USA.|Centrum Wiskunde & Informatica (CWI), Life Sciences Group, Science Park 123, Amsterdam 1098 XG, The Netherlands and Department of Computer Science and Brown University, Providence, Rhode Island 02906, USA.