1. Department of Genetics, The Life Sciences Institute, The Hebrew University of Jerusalem, Jerusalem 91904, 1 and
2. Section of Genetics and Development 2 and
3. Section of Biochemistry, Molecular and Cell Biology, 3 Cornell University, Ithaca, New York 14853;
4. M. E. Mueller-Institute for Microscopy, Biozentrum, University of Basel, Basel, Switzerland 4 ; and
5. Department of Electronics, Jerusalem College of Technology, Jerusalem 91160, 5 Israel;
6. Department of Pharmacological Sciences, Health Sciences Center, State University of New York at Stony Brook, Stony Brook, New York 117946