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We studied the mechanism of ring chromosome 21 (r(21)) formation in 13 patients (11 unique r(21)s), consisting of 7 from five families with familial r(21) and 6 with de novo r(21). The copy number of chromosome 21 sequences in the rings of these patients was determined by quantitative dosage analyses for 13 loci on 21q. Nine of 11 r(21)s, including the 5(More)
In a young male with Fanconi's anaemia, 10% of cells in a direct bone marrow preparation had chromosome abnormalities. Breaks involving primarily groups B and C members constituted the most frequent changes encountered, while 2 cells had either a dicentric or a ring chromosome. Smears from the same aspirate showed anaphase bridges in 3oo of mitoses. It is(More)
The Prader-Willi syndrome is frequently associated with cytogenetic abnormality involving chromosome 15.1 This report presents a new case of this syndrome with the karyotype 45,XX,-15,-19, +der(19),t(15 ;19)(ql2;ql3). The child was born at 8 months' gestation to young, unrelated parents. The mother's first pregnancy resulted in spontaneous abortion after 3(More)
A critical role of the X chromosome in primary determination of sex and fertility has recently been revealed. Studies of deletions of the X chromosome showed that in most cases of Xqaberrations the breaks occur within the critical region Xql3-q27,6 which is responsible for normal ovarian and female sex development. Female patients with deletions of the long(More)