1. Department of Bioinformatics, College of Life Sciences, Zhejiang University, Hangzhou, P.R. China
2. Department of Mathematical Sciences, University of Essex, Essex, England, UK
3. Department of Computer Science, Royal Holloway, University of London, Egham, England, UK
4. Institute of Cytology and Genetics SB RAS, Novosibirsk, Russia
5. Novosibirsk State University, Novosibirsk, Russia