Affiliation: | a Molecular Genetics Section, Division of Biological Sciences, National Research Council, 100 Sussex Drive, Ottawa, Ont., Canada K1A OR6 Tel. (613)990-0816 ** Département de Biochimie, Pavillon Vachon, Université Laval, Québec, Qué., Canada G1K 7P4 Tel. (418)656-5171 |