Molecular analysis of chromosome 21 in a patient with a phenotype of down syndrome and apparently normal karyotype
- Uppsala Univ. (Sweden); and others
Down syndrome (DS) is caused in most cases by the presence of an extra chromosome 21. It has been shown that the DS phenotype is produced by duplication of only a small part of the long arm of chromosome 21, the 21q22 region, including and distal to locus D21S55. We present molecular investigations on a woman with clinically typical DS but apparently normal chromosomes. Her parents were consanguineous and she had a sister with a DS phenotype, who died at the age of 15 days. Repeated cytogenetic investigations (G-banding and high resolution banding) on the patient and her parents showed apparently normal chromosomes. Autoradiographs of quantitative Southern blots of DNAs from the patient, her parents, trisomy 21 patients, and normal controls were analyzed after hybridization with unique DNA sequences regionally mapped on chromosome 21. Sequences D21S59, D21S1, D21S11, D21S8, D21S17, D21S55, ERG, D21S15, D21S112, and COL6A1 were all found in two copies. Fluorescent in situ hybridization with a chromosome 21-specific genomic library showed no abnormalities and only two copies of chromosome 21 were detected. Nineteen markers from the critical region studied with polymerase chain reaction amplification of di- and tetranucleotide repeats did not indicate any partial trisomy 21. From his study we conclude that the patient does not have any partial submicroscopic trisomy for any segment of chromosome 21. It seems reasonable to assume that she suffers from an autosomal recessive disorder which is phenotypically indistinguishable from DS. 23 refs., 6 figs., 3 tabs.
- OSTI ID:
- 478398
- Journal Information:
- American Journal of Medical Genetics, Journal Name: American Journal of Medical Genetics Journal Issue: 4 Vol. 63; ISSN 0148-7299; ISSN AJMGDA
- Country of Publication:
- United States
- Language:
- English
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BASIC STUDIES
BANDING TECHNIQUES
BIOLOGICAL MARKERS
CHROMOSOMAL ABERRATIONS
DETECTION
DNA HYBRIDIZATION
DNA SEQUENCING
DOWNS SYNDROME
FLUORESCENCE
GENETIC MAPPING
GENETICS
HEREDITARY DISEASES
HUMAN CHROMOSOME 21
IN-SITU HYBRIDIZATION
KARYOTYPE
MENTAL DISORDERS
PATIENTS
PHENOTYPE
POLYMERASE CHAIN REACTION
RECESSIVE MUTATIONS