Showing papers on "Ring chromosome published in 1981"

The cytogenetic and clinical implications of a ring chromosome 2.

Abstract: Ring chromosome formation can occur without deletion, through the abnormal pairing of the palindromic DNA base sequences thought to make up the telomeres. The normal occurrence of sister chromatid exchanges within a ring constantly produces further chromosomal anomalies that are less likely to survive when the chromosome involved is large and/or its aneuploidy incompatible with life. These abnormal products (abbreviated pro) were only found in the present case after two or more cell cycles in lymphocyte cultures. Their elimination in vivo implies a very high cellular death rate and an enormous waste of metabolism that should have the same phenotypic effects no matter what chromosome is involved. These phenotypic anomalies form a ring syndrome that can be clinically recognized and consists of severe growth failure, mental retardation and a pleasant personality. The syndrome is usually masked by the more severe abnormalities produced by the deletions present in most cases of ring chromosomes.

Ring chromosome 14: a distinct clinical entity.

Abstract: An infant girl with ring chromosome 14 is presented The findings in this patient and in six previously reported cases of a ring 14 suggest that a characteristic clinical syndrome is associated with this chromosome aberration The major features of the ring chromosome 14 syndrome include mental retardation, a disorder of skin pigmentation, seizures, and dysmorphic features, including flat occiput, epicanthal folds, downward slanting eyes, flat nasal bridge, upturned nostrils, short neck, and large low set ears

Analysis of banding patterns in a case of ring chromosome 21.

Abstract: An infant with psychomotor retardation, hypertonia, microphthalmia, buphthalmos, cleft palate, nail dysplasia, and hypospadias had the karyotype 46,XY, r(21)/45,XY,-21 Cytogenetic analysis of prophase and prometaphase chromosomes showed the breakpoints of chromosome 21 were at p12 and q222

Ring chromosome 11 [46,XX,r(11) (p15q25)] associated with clinical features of the 11q- syndrome.

Abstract: A 2-year-old girl with a ring of chromosome 11[46,XX,r(11)(p15q25)] was reported. Her clinical features included growth and psychomotor retardation, microbrachycephaly, hypertelorism, strabismus externus, short nose, low nasal bridge, low-set ears, microretrognathism, short neck, small opening of vagina with large clitoris, deformity of nails, cafe-au-lait spot of the skin, general hirsutism, congenital heart disease, generalized convulsions, and pancytopenia. Most of these features are those characteristic of the 11q- syndrome. The fact that the patients with the deletion distal from q22 (reported cases) to q25 (our case) had a common phenotype suggests that the loss of the q25 leads to qter segment is mainly responsible for the characteristic clinical features of the 11q- syndrome.

Ring (15) chromosome.

Abstract: Cytogenetic studies on lymphocytes from a girl aged 3 years and 10 months revealed a ring chromosome 15. Several banding methods showed the r(15) chromosome not to have any apparent deletion of the long arm. The silver staining technique for nucleolar organizer regions showed an NOR positive region (band p12). In only a few cells was a chromosome 15 missing. The size of the r(15) was found to be constant. Comparison with 11 previous reported cases in the literature shows that the clinical manifestations in the different patients with ring chromosome 15 are constant although not clinically identifiable and it appears likely to attribute them to a significantly retarded intrauterine and postnatal growth instead of presumed deficiency in the long arm and mosaic configurations.

Structural variation of chromosome 21 and symptoms of Down's syndrome.

Abstract: The analysis of the fine structure of the chromatids permits the identification of different regions on the long arm of chromosome 21. The preponderant role of the distal third of the long arm in the syndrome of trisomy 21 is now well established. Thus, trisomy of only band 21q22 results in a state identical to that caused by complete trisomy 21. If the trisomy involves only a part of band 21q22, the intensity of the symptoms is diminished, but the appearance of the patient is still reminiscent of Down’s syndrome.

Phenotype associated with ring 10 chromosome: Report of patient and review of literature

Abstract: A 15-month-old infant's peripheral blood chromosome analysis showed the following defects: 46,XY,r(10)(p153q261) in 84 cells, 45,XY,-r(10) in 13 cells, and 47,XY,r(10),+r(10) in one cell Clinical abnormalities included growth retardation, microcephaly, prominent nasal bridge, macular hypoplasia, persistent pulmonary hypertension, and posterior urethral valves with hydronephrosis Comparison of the phenotype of five other patients with a ring chromosome 10 with the present case showed the following common manifestations: growth retardation, microcephaly, undescended testes, hydronephrosis, and, in males, posterior urethral valves To date, this last anomaly has not been seen in patients with either a del(10p) or a del(10q) abnormality

Ring chromosome 16.

Abstract: Ring chromosome 16 was found in a 33-year-old woman with mental, motor, and growth defects. Apart from a low percentage of monosomy 16 cell lines, the patient appears to have virtually all of the normal chromosome 16 genetic material at the microscopic level. Her impressive problems highlight the limitation of our ability to detect small deletions and the profound importance of the integrity of chromosome 16 in normal human development.

Study of two cases of ring 13 chromosome using high-resolution banding.

Abstract: The chromosomes of two patients with ring 13 (r13) were studied using high-resolution RBG banding of prometaphase cells. The rings of the two patients differ slightly in breakpoints. Cell with multiple single, double-sized rings, quadruple-sized rings, rod- and ring-shaped fragments, and fragments showing varied states of condensation were seen, as were cells monosomic for chromosome 13. The evolution of these cell lines as a result of sister chromatid exchange, nondisjunction, ring breakage, and premature chromosome condensation is discussed. Clinical features of these patients reflect the heterogeneity of phenotype for r13 patients. Each case includes a feature of trisomy 13. The significance of mosaicism of cell lines in patients bearing ring chromosomes is considered with respect to variation in clinical findings.

Ring chromosomes in barley (Hordeum vulgare L.)

Abstract: A plant with 2n = 14 + 1 ring chromosomes was obtained in the progeny of a primary trisomie for chromosome 7 of a two-rowed cultivar, Shin Ebisu 16. The morphological characteristics of the trisomic plants with an extra ring chromosome were similar to the primary trisomic for chromosome 7 (Semierect), which suggests that it originated from this chromosome. The ring chromosomes were not completely stable in mitotic cells because of abnormal behavior. Chromosome complements varied in different plants and in different roots within a plant. Root tip cells and spikes with 2n = 14 and 14 + 2 ring chromosomes were observed on plants with 14 + 1 ring chromosomes. Breakage-fusion-bridge cycle was inferred. The ring chromosome was associated with two normal homologues forming a trivalent in 17.6% sporocytes at metaphase I. The transmission of the extra ring chromosome was 23.1% in the progeny of the plant with 14 + 1 ring chromosomes. Trivalent formation may have been much higher at early prophase stages which were difficult to analyze in barley; only 4 of 120 sporocytes analyzed showed an isolated ring at pachytene. The ring chromosome moved to one pole without separation in 24.7% of the sporocytes at AI, and divided in 27.1% sporocytes giving rise to 8-8 separation. Only 10% of the sporocytes showed bridge formation at AI.

Two cases of ring chromosome 13. Chromosome banding patterns and mosaic configuration.

Abstract: Two ring chromosomes 13 were studied by means of various cytogenetic techniques in two psychomotorically retarded male infants. Common features of our patients include microcephalia, hypertelorism, wide and prominent nose bridge, and cryptorchism. Various configurations of the aberrant chromosomes could be identified in cultured skin fibroblasts and peripheral lymphocytes from both patients. Chromosome heteromorphisms and analysis of silver stained nucleolus organizer regions (Ag-NOR) substantiated the parental origin of the ring chromosomes. The more severely affected patient showed a break point at band 13q32 in the long arm of the ring, whereas in the less severely affected the loss of material during ring formation was restricted to the telomere. This provides further evidence for a clinical relevance of the detected mosaic configurations of the rings.

Ring chromosome 5 with dental anomalies.

Abstract: Although ring chromosomes are observed in ahnost all autosomal groups in man, they are rare. We describe a male patient exldbiting cd du chat syndrome in which cytogenetic studies demonstrate he presonse of a ring chromosome 5. Deletion o£ the ring chromosome 5 is found between the p15 and q35 bands. Dental, medical and cytogenetic findings are compared to other ring chromosome 5 cases descMbed in literature.

[45X/46XY/46XrY mosaic with banding and the Turner phenotype (author's transl)].

Abstract: A chromosome make-up of 45X/46XY can be associated with gonadal dysgenesis, partial dwarfism and Turner-like congenital abnormalities according to Simpson's terminology, as can pure 45X. The Turner syndrome in the form of X/XY is rare. There is a double interest in the case that we report apart from its rarity; first because it has been possible to show lack fluorescence of the Y chromosome which can occur in the pathogenesis of clinical manifestations, when a third clone exists as an addition together with a ring chromosome Y. Because the risks of tumours developing are great when the caryotype includes a Y even if it is one with banding the adnexae should be removed routinely in these cases. A tumour can develop in these girls whereas there is practically no risk if the caryotype is 45X or a mosaic without a Y in it.