Cases reported "Nondisjunction, Genetic"

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1/16. angelman syndrome with uniparental disomy due to paternal meiosis II nondisjunction.

    We report a case of angelman syndrome (AS) with paternal uniparental disomy (pUPD) of chromosome 15. This 6-year-old girl with overgrowth had frequent, but only provoked laughter, was mildly ataxic with limb hypertonia, and had no intelligible speech. She had deep-set eyes, protruding tongue, and prominent chin. The karyotype was normal. dna analysis with microsatellites from chromosome 15 showed no inheritance of maternal alleles both within and outside the AS critical region. Proximal markers showed reduction to homozygosity of paternal alleles, intermediate markers showed nonreduction, and distal markers reduction, thus suggesting a meiosis II nondisjunction event in the father with two crossovers. This is, to our knowledge, the first reported case of AS due to meiosis II nondisjunction. We present detailed physical measurements in this patient, adding to the clinical description of the milder phenotype in AS due to pUPD.
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2/16. Recurrent triploidy of maternal origin.

    We report the occurrence of triploid preimplantation embryos following in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI) in a woman with two previously-identified triploid conceptuses which spontaneously underwent fetal demise at 10 and 23 weeks' gestation. An error in maternal meiosis II is proposed as the most likely cause.
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3/16. Meiotic behaviour of the sex chromosomes in three patients with sex chromosome anomalies (47,XXY, mosaic 46,XY/47,XXY and 47,XYY) assessed by fluorescence in-situ hybridization.

    Meiotic studies using multicolour fluorescent in-situ hybridization (FISH) and chromosome painting were carried out in three patients with sex chromosome anomalies (47,XXY; 46,XY/47,XXY and 47,XYY). In the two patients with klinefelter syndrome, although variable percentages of XXY cells (88.5 and 28.3%) could be found in the pre-meiotic stages, none of the abnormal cells entered meiosis, and all pachytenes were XY. However, the abnormal testicular environment of these patients probably resulted in meiotic I non-disjunction, and a certain proportion of post-reductional cells were XY (18.3 and 1.7%). The fact that none of the spermatozoa were XY also suggests the existence of an arrest at the secondary spermatocyte or the spermatid level. In the XYY patient, most (95.9%) premeiotic cells were XYY. The percentage of XYY pachytenes was 57.9%. The sex chromosomes were either in close proximity (XYY) or the X chromosome was separated from the two Ys (X YY). A high proportion (42.1%) of post-reductional germ cells were XY. However, only 0.11% of spermatozoa were disomic for the sex chromosomes. In this case, the data suggest the existence of an arrest of the abnormal cells at the primary and the secondary spermatocyte or the spermatid level, giving rise to the continuous elimination of abnormal cells in the germ-cell line along spermatogenesis. The fact that the proportion of diploid spermatozoa was only increased in one of the three cases (XXY) is also suggestive of an arrest of the abnormal cell lines in these patients. The two apparently non-mosaic patients were, in fact, germ-cell mosaics. This suggests that the cytogenetic criteria used to define non-mosaic patients may be inadequate; thus, the risk of intracytoplasmic sperm injection in apparently non-mosaics may be lower than expected.
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4/16. Constitutional trisomy 8 mosaicism due to meiosis II non-disjunction in a phenotypically normal woman with hematologic abnormalities.

    Constitutional trisomy 8 mosaicism (CT8M) in liveborns is typically caused by mitotic non-disjunction and exhibits wide phenotypic variability. By contrast, CT8M due to meiotic errors usually results in miscarriage. We describe a case of CT8M due to a paternal meiosis II non-disjunction error. The patient, a 32-year-old woman, was phenotypically normal except for a history of recurrent aphthous ulcers since childhood and a 4-year history of macrocytosis. The ulcers were refractory to steroids, but responded well to thalidomide. To the best of our knowledge, this is the first report of CT8M due to meiotic non-disjunction in a phenotypically normal individual.
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keywords = meiosis
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5/16. Parental origin and mechanism of formation of polysomy X: an XXXXX case and four XXXXY cases determined with RFLPs.

    The parental origin and mechanism of formation of polysomy X were studied in five cases (one case of 49,XXXXX; four cases of 49,XXXXY), using various X-linked restriction fragment length polymorphisms as genetic markers. Segregation and densitometric analyses on the polymorphic dna fragments revealed that, in all five cases, the additional X chromosomes are of maternal origin and the mechanism of formation is most probably a result of three non-disjunctions during maternal meiotic divisions: once at the first meiosis and simultaneously twice at the second meiosis. The identical origin and the identical mechanism of formation among the five cases are unlikely to be coincidental and suggest a common cause in the mothers of the five cases.
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keywords = meiosis
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6/16. The unbalanced offspring of the male carriers of the 11q;22q translocation: nondisjunction at meiosis II in a balanced spermatocyte.

    Carriers of the standard translocation t(11;22) (q23.3;q11.2) produce only one type of unbalanced offspring, a tertiary trisomy resulting into the karyotype 47,XX or XY, der(22)t(11;22)(q23.3;q11.2), usually derived from the mother. The exception is one single patient 47,XY,t(11;22)(q23.3;q11.2), der(22)t(11;22) (q23.3;q11.2)pat. We report a second case with the same karyotype, also of paternal origin. Thus, the rare unbalanced offspring of a carrier father (only 5 cases known) may receive a supernumerary der(22), as a consequence of tertiary trisomy, but also as a consequence of nondisjunction at meiosis II of a balanced spermatocyte.
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7/16. Maternal meiosis II nondisjunction in a case of 47,XXY testicular feminization.

    An 11-year-old patient with incomplete testicular feminization and a 47,XXY karyotype is described. The patient had female external genitalia, clitoromegaly, and some features of Klinefelter's syndrome, including speech delay and delayed intellectual development. dna analysis using X chromosomal dna sequences suggest that the supernumerary X chromosome in the patient resulted from maternal nondisjunction during meiosis II. The M II error thereby provides the basis for homozygosity of a mutation in the androgen receptor locus.
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keywords = meiosis
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8/16. Coincident maternal meiotic nondisjunction of chromosomes X and 21 without evidence of autosomal asynapsis.

    A family in which the proband showed phenotypic signs of both the Turner and Down syndromes was studied cytogenetically and with restriction fragment length polymorphisms. The proband's karyotype was 46,X, 21, showing double aneuploidy without any signs of mosaicism. The single X and one chromosome 21 were of paternal origin while two chromosome 21 were of maternal origin. The nondisjunction of chromosome 21 took place in maternal meiosis II. If it is assumed that the absence of mosaicism renders postzygotic mitotic loss of the X chromosome unlikely, then the X chromosome would have been lost in maternal meiosis I or II. Recombination had occurred between the nondisjoined chromosomes 21. We conclude that double nondisjunction took place in one patient and that asynapsis was not a prerequisite for the autosomal nondisjunction.
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keywords = meiosis
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9/16. An XXX male resulting from paternal X-Y interchange and maternal X-X nondisjunction.

    A 2-year-old boy was found to have a 47,XXX karyotype. Restriction-fragment-length-polymorphism analysis showed that, of his three X chromosomes, one is of paternal and two are of maternal origin. The results of Y-dna hybridization were reminiscent of those in XX males in two respects. First, hybridization to Southern transfers revealed the presence in this XXX male of sequences derived from the Y-chromosomal short arm. Second, in situ hybridization showed that this Y dna was located on the tip of the X-chromosomal short arm. We conclude that this XXX male resulted from the coincidence of X-X nondisjunction during maternal meiosis and aberrant X-Y interchange either during or prior to paternal meiosis.
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keywords = meiosis
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10/16. Cytogenetic and molecular studies of trisomy 13.

    Chromosome heteromorphisms, restriction fragment length polymorphisms, or both were used to study the parental origin of 33 cases of simple trisomy 13 and eight cases of translocation trisomy 13. The most common origin for the simple trisomies was non-disjunction at maternal meiosis I, while for the translocations an equal number of paternally and maternally derived cases was observed. In seven of the simple trisomies, information was obtained from both the cytogenetic and molecular markers, making it possible to study recombination between the two non-disjoined chromosomes. Five of the seven cases involved errors at meiosis I, with crossing over being detected in two of three cases of maternal origin and in one of two cases of paternal origin. This indicates that absence of recombination because of pairing failure is unlikely to be of major importance in the genesis of trisomy 13.
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