The Bioinformatics Centre, Department of biology, University of Copenhagen, 2200 Copenhagen N, Denmark. andersbj@binf.ku.dk|The Bioinformatics Centre, Department of biology, University of Copenhagen, 2200 Copenhagen N, Denmark. andersbj@binf.ku.dk|The Bioinformatics Centre, Department of biology, University of Copenhagen, 2200 Copenhagen N, Denmark. andersbj@binf.ku.dk|The Bioinformatics Centre, Department of biology, University of Copenhagen, 2200 Copenhagen N, Denmark. andersbj@binf.ku.dk