title: Two brothers with mental retardation discordant for the fragile-X syndrome.
abstract: We describe two male sibs with mental retardation discordant for the fragile-X syndrome. In the younger sib, chromosome analysis under folate deprivation showed a fragile site at Xq27.3 in 12-46% of mitoses. In the older sib, however, repeated chromosome analyses (six different cultures with analysis of 50 mitoses each) under identical conditions could not detect any fragile-X site. Using DNA probes linked to the fragile-X gene, we found evidence that the two sibs inherited a different maternal X chromosome at Xq27.3. This excluded the presence of the fragile-X syndrome in the older sib with a probability of greater than 99%.
authors.affiliation: Department of Medical Genetics, University of Antwerp-UIA, Wilrijk, Belgium.
authors.forename: B C
authors.initials: BC
authors.lastname: Van Roy
authors.forename: P J
authors.initials: PJ
authors.lastname: Willems
authors.forename: L J
authors.initials: LJ
authors.lastname: Vits
authors.forename: B P
authors.initials: BP
authors.lastname: Ceulemans
authors.forename: P J
authors.initials: PJ
authors.lastname: Coucke
authors.forename: B J
authors.initials: BJ
authors.lastname: Van der Auwera
authors.forename: J A
authors.initials: JA
authors.lastname: Lormans
authors.forename: J E
authors.initials: JE
authors.lastname: Dumon
mesh_terms: D000328:Adult; D002648:Child; D004247:DNA / Q000032:analysis; D015342:DNA Probes; D005600:Fragile X Syndrome / Q000235:genetics*; D006801:Humans; D008607:Intellectual Disability / Q000235:genetics*; D008297:Male; D010375:Pedigree; D010641:Phenotype; D012729:Sex Chromosome Aberrations / Q000235:genetics*
chemical_list: D015342:DNA Probes; D004247:DNA