1. School of Life Sciences, University of Essex, Wivenhoe Park, Colchester CO4 3SQ, UK
2. Biological Sciences BSc Program, University of Essex, Wivenhoe Park, Colchester CO4 3SQ, UK
3. Wellcome Trust Vacation Student
4. Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA