- Identification of molecular defects causing congenital adrenal hyperplasia by cloning and differential hybridization of polymerase chain reaction-amplified 21-hydroxylase (CYP21) genes. Helmberg, A., Tabarelli, M., Fuchs, M.A., Keller, E., Dobler, G., Schnegg, I., Knorr, D., Albert, E., Kofler, R. DNA Cell Biol. (1992)