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A large family with subtelomeric translocation t(18;21)(q23;q22.1) and molecular breakpoint in the Down syndrome critical region |
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| Authors: | O Bartsch Georg K Hinkel Michael B Petersen Ulrich König Merete Bugge Margareta Mikkelsen Dimitris Avramopoulos Michael Morris Stylianos E Antonarakis |
| Institution: | Department of Clinical Genetics, Hospital “Carl Gustav Carus”, Technical University, Fetscherstrasse 74, D-01307 Dresden, Germany Fax: +49-351-458-5385, DE Department of Medical Genetics, The John F. Kennedy Institute, DK-2600 Glostrup, Denmark, DK Department of Genetics, Institute of Child Health, “Aghia Sophia” Children’s Hospital, GR-11527 Athens, Greece, GR Division de Génétique Medicale, H?pital Universitaire, CH-1211 Genéve 14, Switzerland, CH |
| Abstract: | We describe a 17-month-old infant with clinical features of Down syndrome and a normal karyotype by standard chromosomal analysis, her two uncles aged 28 and 30 years, respectively, with reduced intelligence and unusual appearance but not apparent Down syndrome, and a severely retarded 6-year-old girl with dysmorphy and epilepsy from the same family. Cytogenetic studies of patients and normal intervening relatives had been carried out at different institutions with normal results. Fluorescence in situ hybridization using whole chromosome painting and unique-copy probes (cosmids) and high-resolution banding revealed a familial subtelomeric translocation of chromosomes 18 and 21, resulting in partial trisomy 21 in the infant and her two uncles, and partial monosomy 21 in the 6-year-old girl. Cytogenetic breakpoints were located in bands 18q23 and 21q22.1, respectively. The molecular breakpoint on chromosome 21 was located between D21S211 (proximal) and D21S1283 (distal) and thus maps within the Down syndrome critical region. Received: 11 November 1996 / Accepted: 29 April 1997 |
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