PRENATAL-DIAGNOSIS OF THE DERIVATIVE CHROMOSOME-22 ASSOCIATED WITH CAT EYE SYNDROME BY FLUORESCENCE IN-SITU HYBRIDIZATION

Cytogenetic studies of cultured amniocytes demonstrated a karyotype of 46,XX/47,XX,+mar. A bisatellited, dicentric, distamycin-DAPI negative , NOR-positive marker was present in 76 per cent of the metaphases exa mined. Similar markers have been associated with cat eye syndrome (CES ). We report on the utilization of fluorescence in situ hybridization (FISH) with a 14/22 alpha-satellite probe and a chromosome 22-specific cosmid for locus D22S9 to determine the origin of the prenatally dete cted supernumerary marker chromosome. FISH studies demonstrated that t he marker is a derivative of chromosome 22 and enabled us to provide t he family with additional prognostic information.