Rapid progress has been made in the analysis of the fragile X syndrome during 1991. Different groups have discovered that fragile X chromosomes are preferentially methylated. In these X chromosomes an insertion has been found in the methylated region. The FMR-1 gene, the transcription of which is shut off in patients, has been isolated. The expansion found in fragile X chromosomes is localized in the coding region of the FMR-1 gene. The fragile X syndrome results from mutations in a (CGG)n repeat found in the coding region of the FMR-1 gene. It will be crucial to determine the FMR-1 protein product in order to learn more about the function of the gene. Diagnosis of the unstable region by DNA analysis is now available as an efficient and reliable test for the diagnosis of carriers, as well as for prenatal diagnosis.,
Chromosoma: biology of the nucleus
Department of Pathology

Oostra, B.A, & Verkerk, A. (1992). The fragile X syndrome: Isolation of the FMR-1 gene and characterization of the fragile X mutation. Chromosoma: biology of the nucleus (Vol. 101, pp. 381–387). doi:10.1007/BF00582832