Affiliation: | From the ‡Institute of Genetics and Animal Breeding, Polish Academy of Sciences, Jastrzębiec, 05-552 Wólka Kosowska, Poland.;the §Institut de Chimie des Substances Naturelles, UPR2301 Centre National de la Recherche Scientifique, Centre de Recherche de Gif, 91190 Gif-sur-Yvette, France, and ;the ¶European Molecular Biology Laboratory, Meyerhofstrasse 1, 69117 Heidelberg, Germany |