Sklower Brooks S, Cohen I, Ferrando C, Jenkins E C, Brown W T, Dobkin C
Department of Human Genetics, New York State Office of Mental Retardation and Developmental Disability, Staten Island 10314.
Am J Med Genet. 1991 Feb-Mar;38(2-3):370-3. doi: 10.1002/ajmg.1320380242.
We investigated the family of a 3-year-old boy with manifestations of the Martin-Bell syndrome (MBS). His 17-year-old cousin had classic manifestations of MBS and was fragile X [fra(X)] positive. The 3-year-old boy was fra(X) negative. Linkage analysis with probes flanking the fra(X) region indicated that these cousins had the same X chromosome inherited from a normal grandfather. The DNA and cytogenetic analyses suggest that limitations in the ability to detect the fra(X) mutation cytogenetically may be responsible for fra(X)-negative MBS; or, alternatively, that a crossover occurred between a locus determining the MBS phenotype and one determining fra(X) expression.
