- Cytological mapping of the human glucose-6-phosphate dehydrogenase gene distal to the fragile-X site suggests a high rate of meiotic recombination across this site. Szabo, P., Purrello, M., Rocchi, M., Archidiacono, N., Alhadeff, B., Filippi, G., Toniolo, D., Martini, G., Luzzatto, L., Siniscalco, M. Proc. Natl. Acad. Sci. U.S.A. (1984)