Molecular diagnosis of fragile X syndrome is usually performed using Southern blot analysis of DNA digested with EcoRI. In the course of diagnostic studies, we observed that a specific EcoRI restriction site in the fragile X gene (FMR1) is sometimes refractory to digestion, generating additional fragments on a Southern blot suggestive of a full mutation in FMR1. This may lead to a false-positive diagnosis of fragile X syndrome. Such additional bands are avoided by the use of HindIII instead of EcoRI. Therefore, we recommend the use of HindIII for the molecular diagnosis of fragile X syndrome.,
Human Genetics
Department of Clinical Genetics

Storm, K., Handig, I., Reyniers, E., Oostra, B., Kooy, F., & Willems, P. (1998). Incomplete EcoRI digestion may lead to false diagnosis of fragile X syndrome. Human Genetics, 102(1), 54–56. doi:10.1007/s004390050653