We report on a family in which a daughter is described with mental retardation, as well as malformations of the heart, and of the brain (Dandy-Walker variant). The patient’s phenotype suggests a chromosomal rearrangement. However, her karyotype was unremarkable by conventional cytogenetic analysis. In order to detect chromosome rearrangements overseen by this method, the subtelomere regions of suspicious chromosomes were verified by fluorescence in situ hybridization (FISH). A rearranged derivative chromosome 6 was identified. Further examinations by FISH-microdissection (FISH-MD) revealed a maternal complex balanced translocation. The patient inherited the derivative chromosome 6 from her mother and therefore carries a partial monosomy 6q26→qter and a partial trisomy 11q23.3→qter.
A patient with a deletion of the distal portion of the long arm (q21) of chromosome Y is described clinically and cytogenetically. The proband has a normal male habitus but with azoospermia. The proband was investigated because of infertility. Male relatives were also investigated cytogenetically. The deleted Y chromosome was measured and compared with the normal Y of male family members. The results suggest that no Y euchromatin was lost.
Karyotyped specimens of peripheral blood from 1,055 chromosomally normal individuals (573 females, 482 males) presenting with habitual spontaneous abortion were examined for aneuploidy. Trisomy 21 was noted in six of 14,802 cells. These data were not significantly different from those obtained on chromosomes 19 and 20, or the data obtained from three different, smaller, control groups. The low rate of trisomy 21 cells found in this study suggests that we cannot extrapolate from events in somatic cells in mitosis to nondisjunction events in meiosis.
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