1/25. Chromosome duplications and deletions and their mechanisms of origin.Duplications and deletions of the same gene loci or chromosome regions are known to produce different clinical manifestations and are significant factors in human morbidity and mortality. Extensive cytogenetic and molecular cytogenetic studies with cosmid and YAC probes in two patients with unique mosaicism for reciprocal duplication-deletion allowed us to further understand the origin of these abnormalities. The first patient's mosaic karyotype was 46,XX, inv dup(11) (q23q13)/46,XX,del(11)(q13q23). The second patient had a 46,XY,dup(7)(p11.2p13)/46,XY,del(7)(p11.2p13)/46,XY karyotype. fluorescence in situ hybridization studies on the first patient placed the two breakpoints near the folate-sensitive fragile sites FRA11A and FRA11B. The presence of repeated sequences responsible for these fragile sites may have been involved in the patient's duplication-deletion. Our investigation leads us to conclude that, in addition to known mechanisms (such as unequal crossovers between homologs, unequal sister chromatid exchanges, excision of intrachromatid loops, and meiotic recombination within a single chromatid), duplication-deletion can also arise by the formation of an overlying loop followed by an uneven crossover at the level of the dna strand.- - - - - - - - - - ranking = 1keywords = hybridization (Clic here for more details about this article) |
2/25. Supernumerary chromosome inherited from a maternal balanced translocation leading to pure trisomy 9p.We describe a child with a supernumerary chromosome defined as der(9)t(9;22) (q12;p11), resulting in trisomy 9p and trisomy 22p. The mother carried the balanced translocation. In G- and C-banding the derivative chromosome 9 appeared to be dicentric and to contain 22q material. Using in situ hybridization we defined the exact breakpoints of the translocation and ruled out the possibility of a centric fission in the mother's chromosomes.- - - - - - - - - - ranking = 1keywords = hybridization (Clic here for more details about this article) |
3/25. Ring chromosome 7 and sacral agenesis.A ring chromosome 7 was found in a 19-month-old girl with microcephaly, growth and developmental delay, multiple angiomas, and partial sacral agenesis. Absent sacrum is a frequent finding in patients with 7q terminal deletions; in fact, genes involved in the sacral agenesis are localized in 7q36. However, this anomaly was not described previously in patients with a ring chromosome 7. High resolution G-banding chromosome and fluorescence in situ hybridization (FISH) demonstrated that our patient lost this region during ring formation.- - - - - - - - - - ranking = 1keywords = hybridization (Clic here for more details about this article) |
4/25. Mosaic r(13) resulting in large deletion of chromosome 13q in a newborn female with multiple congenital anomalies.A newborn female presented with multiple congenital anomalies including facial dysmorphism, agenesis of the corpus callosum, type I laryngeal cleft, tracheal stenosis, bilaterally small kidneys, segmental vertebral anomalies, extranumerary rib, bilateral hip dislocation, digital anomalies, and growth retardation. Newborn aneuploidy detection (nad) based on interphase fluorescence in situ hybridization (FISH) indicated monosomy 13 in 47 of 200 (23.5%) peripheral blood cells (normal cutoff 8.5% at 95% CI). The follow-up banded metaphase-based analysis of 20 cells revealed a karyotype of 46,XX. The analysis of 30 additional cells revealed one cell to have monosomy 13 and a small ring chromosome. In the abnormal cell line, the ring was positive for whole chromosome paint (wcp) 13 and negative for Rb1 (13q14.3). The ring was detected in 4% of 80 additional metaphases studied by FISH. Therefore, the ring was present in 4% (5/130) of metaphases from peripheral blood. Analysis of buccal cells by FISH indicated the ring was present in 36% of cells. A higher degree of mosaicism (60%) was detected in fibroblast cultures from a skin biopsy. The low-level mosaicism of ring 13 in metaphase cells from peripheral blood would have been missed if the standard 20 GTL-banded metaphases had been analyzed. In this case, a preliminary interphase FISH study had indicated monosomy 13 resulting from a large 13q deletion that included the Rb1 locus. This finding initiated the analysis of additional metaphases by GTL-banding and the analysis of metaphases and interphases by FISH. The clinical presentation of our patient was consistent with reported cases of 13q deletions. In addition, our patient had airway anomalies, including a type I laryngeal cleft and tracheal stenosis, which are previously unreported.- - - - - - - - - - ranking = 1keywords = hybridization (Clic here for more details about this article) |
5/25. Duplication of (2)(q11.1-q13.2) in a boy with mental retardation and cleft lip and palate: another clefting gene locus on proximal 2q?A 4-year-old boy with left cleft lip and cleft palate, multiple minor anomalies and developmental delay revealed an abnormal chromosome 2 with enlarged proximal long arm, de novo, in his karyotype. fluorescence in situ hybridization with a chromosome 2 library and band-specific YACs confined the duplicated segment to 2q11.1-q13.2 and indicated a direct tandem duplication due to unbalanced crossover between chromatids.- - - - - - - - - - ranking = 1keywords = hybridization (Clic here for more details about this article) |
6/25. Oligoyric microcephaly in a child with williams syndrome.We report a 19-month-old boy with microcephaly, growth and developmental delay, facial dysmorphisms, and simplified gyral pattern. magnetic resonance imaging (MRI) examination demonstrated microcephaly with simplified gyral pattern or oligogyric microcephaly. The facial phenotype was interpreted as suggestive of williams syndrome (WS). fluorescence in situ hybridization (FISH) analysis performed with an elastin probe revealed a deletion in the chromosomal band 7q 11.23, confirming the clinical diagnosis. To our knowledge, this represents the first patient with WS and oligogyric microcephaly.- - - - - - - - - - ranking = 1keywords = hybridization (Clic here for more details about this article) |
7/25. prenatal diagnosis of de novo terminal deletion of chromosome 7q.OBJECTIVES: To present the prenatal diagnosis and perinatal findings of a de novo terminal deletion of chromosome 7q. CASE: amniocentesis was performed at 21-weeks gestation owing to a positive result of maternal serum multiple-marker screening. The 30-year-old woman, gravida 2, para 1, had a maternal serum multiple-marker screening test at 18-weeks gestation. The risk of down syndrome was 1/11 calculated from the gestational age, maternal age, a maternal serum alpha-fetoprotein level of 1.026 multiples of the median (MOM), and a maternal serum free beta-human chorionic gonadotrophin (hCG) level of 8.678 MoM. cytogenetic analysis of the cultured amniotic fluid cells revealed a de novo terminal deletion of 7q, 46,XX,del(7)(q35). ultrasonography showed intrauterine growth restriction, microcephaly, and tetralogy of fallot. The pregnancy was terminated subsequently. Grossly, the placenta was normal. On autopsy, the proband additionally manifested a prominent forehead, hypertelorism, epicanthus, upslanting palpebral fissures, a flat and broad nasal bridge, micrognathia, large low-set ears, overriding toes, and a normal brain. radiography demonstrated a normal spine. fluorescence in situ hybridization analysis demonstrated a 7q terminal deletion. Genetic marker analysis showed a maternally derived terminal deletion of chromosome 7(q35-qter). CONCLUSION: Fetuses with a de novo 7q terminal deletion may be associated with a markedly elevated maternal serum hCG level and abnormal sonographic findings of intrauterine growth restriction, microcephaly, and congenital heart defects in the second trimester.- - - - - - - - - - ranking = 1keywords = hybridization (Clic here for more details about this article) |
8/25. Putative monosomy 21 in two patients: clinical findings and investigation using fluorescence in situ hybridization.Complete monosomy 21 is claimed to be a rare chromosomal disorder in which the cytogenetic investigation is bedevilled by technical difficulties. We describe the disparate clinical features in two patients in whom an initial diagnosis of monosomy 21 was made by routine karyotyping. fluorescence in situ hybridisation (FISH) confirmed a translocation of chromosome 21 material to the short arm of chromosome 5 and to the x chromosome, respectively. The usefulness of FISH in the investigation of subtle chromosomal rearrangements is hereby demonstrated. These findings also cast doubt on the existence of "pure" monosomy 21 as an entity, and suggest that partial monosomy 21 is a more likely occurrence.- - - - - - - - - - ranking = 4keywords = hybridization (Clic here for more details about this article) |
9/25. microcephaly, jejunal atresia, aberrant right bronchus, ocular anomalies, and XY sex reversal.We present a patient with microcephaly, jejunal atresia, aberrant right tracheobronchial tree, mild left blepharoptosis, and corectopia (irregular pupil), left sectoral iris stromal hypoplasia and peripheral anterior synechia, and 46,XY sex reversal. Testosterone and dihydrotestosterone (DHT) levels were within normal limits for a male infant at 3 weeks of age. Gonadectomy at age 18 months revealed immature testis tissue and no evidence of Mullerian structures. PCR amplification of the androgen receptor (AR) gene and flanking genomic regions revealed no evidence for deletion. Array-comparative genomic hybridization (array-CGH) for assessment of gene dosage in other regions of the genome was normal. This patient represents a multiple anomaly disorder similar to intestinal atresia-ocular anomalies-microcephaly syndrome (MIM#243605) but incorporating 46,XY sex reversal with testicular tissue, demonstrating a defect in the sexual differentiation pathway.- - - - - - - - - - ranking = 1keywords = hybridization (Clic here for more details about this article) |
10/25. Inherited ring chromosome 8 without loss of subtelomeric sequences.We report the first case of inherited ring chromosome 8 syndrome without loss of subtelomeric sequences. The proband is a 6 1/2-year-old boy with short stature, microcephaly, mild mental retardation, and behavioral problems including hyperactivity and attention deficit. His mother presented the same physical features but intelligence was normal. family history also revealed an uncle and a grandmother, with short stature and microcephaly. Moderate mental retardation was reported in the uncle. Karyotypes and fluorescence in situ hybridization (FISH) analyses were performed on peripheral blood lymphocytes for both child and mother. The child's karyotype was reported as 46,XY,r(8)(p23q24.3)[24]/45,XY,-8[2] and the mother's karyotype 46,XX,r(8)(p23q24.3)[22]/45,XX,-8[2]/47,XX,r(8)(p23q24.3), r(8)(p23q24.3)[1]. FISH studies showed no deletion of subtelomeric sequences for both child and mother indicating that no or little chromosomal euchromatic material has been deleted. These findings indicate that ring chromosome 8 without loss of subtelomeric sequences can be inherited and that carriers in a same family present with cognitive function ranging from mild mental retardation to normal intelligence.- - - - - - - - - - ranking = 1keywords = hybridization (Clic here for more details about this article) |
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