title: Characterization of a small supernumerary ring X chromosome by fluorescence in situ hybridization.
abstract: We report on a male with mild learning disabilities who has a supernumerary marker chromosome. The marker chromosome was defined by fluorescence in situ hybridization as a ring X chromosome with breakpoints in the juxacentromeric region. Replication studies suggest that the ring X is late-replicating. However XIST, a gene in the X inactivation centre interval which is expressed exclusively from the inactive X chromosome, is not present on the marker, nor is it expressed in the patient's cells. These results are discussed with respect to karyotype-phenotype correlations and X inactivation.
authors.affiliation: Department of Pathology, Queen's University, Kingston, Ontario, Canada.
authors.forename: A M
authors.initials: AM
authors.lastname: Duncan
authors.forename: A
authors.initials: A
authors.lastname: Macdonald
authors.forename: C J
authors.initials: CJ
authors.lastname: Brown
authors.forename: D
authors.initials: D
authors.lastname: Wolff
authors.forename: H F
authors.initials: HF
authors.lastname: Willard
authors.forename: B
authors.initials: B
authors.lastname: Sutton
mesh_terms: D001483:Base Sequence; D002648:Child; D017931:DNA Primers; D004303:Dosage Compensation, Genetic; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D007621:Karyotyping; D008297:Male; D008969:Molecular Sequence Data; D010641:Phenotype; D012303:Ring Chromosomes; D014960:X Chromosome
chemical_list: D017931:DNA Primers