Centrum Wiskunde & Informatica, Life Sciences Group, Amsterdam, The Netherlands. tm@cwi.nl|Centrum Wiskunde & Informatica, Life Sciences Group, Amsterdam, The Netherlands. tm@cwi.nl|Centrum Wiskunde & Informatica, Life Sciences Group, Amsterdam, The Netherlands. tm@cwi.nl|Centrum Wiskunde & Informatica, Life Sciences Group, Amsterdam, The Netherlands. tm@cwi.nl|Centrum Wiskunde & Informatica, Life Sciences Group, Amsterdam, The Netherlands. tm@cwi.nl|Centrum Wiskunde & Informatica, Life Sciences Group, Amsterdam, The Netherlands. tm@cwi.nl|Centrum Wiskunde & Informatica, Life Sciences Group, Amsterdam, The Netherlands. tm@cwi.nl