Ring chromosome

About: Ring chromosome is a research topic. Over the lifetime, 1546 publications have been published within this topic receiving 31061 citations. The topic is also known as: supernumerary circular chromosome.

Supernumerary small ring chromosome.

Abstract: The chromosome analysis of a 10-year-old boy with the clinical symptoms of cheilo-palato-gnatho-schisis and debility revealed an extra small chromosome fragment in most of his cells. Mosaicism of karyotypes has led to the suggestion that the extra chromosome could be a minute ring chromosome. The occurrence of anaphase bridges and micronuclei gave the further evidence of the ring nature of this extra chromosome. Because of its minuteness, the origin of the extra chromosome was not determinable. A comparison of clinical symptoms with those of other known trisomy syndromes is not feasible. Due to the special behavior of the ring chromosome resulting in its gradual elimination, it is supposed that the percentage of euploid cells increases at the same rate.

Stability of monocentric and dicentric ring minichromosomes in Arabidopsis

Abstract: A dicentric ring minichromosome (miniδ) was identified in transgenic Arabidopsis thaliana and added to a wild type as a supernumerary chromosome. This line is relatively stable and has been maintained for generations, notwithstanding its ring and dicentric structure. To determine the mechanism for stable transmission of miniδ, the structure and behavior of two new types of ring minichromosomes (miniδ1 and miniδ1-1) derived from miniδ were investigated. Fluorescence in situ hybridization analysis revealed that miniδ1 is dicentric just like miniδ, whereas miniδ1-1 is monocentric. The estimated sizes of miniδ1 and miniδ1-1 were 3.8~5.0 and 1.7 Mb, respectively. The sizes of the two centromeres on miniδ1 were identical (ca. 270 kb) and similar to that of miniδ1-1 (ca. 250 kb). Miniδ1 was relatively stable during mitosis and meiosis, as is miniδ, whereas miniδ1-1 was unstable during mitosis, and the number of minichromosomes per cell varied. This possibly resulted from misdivision caused by a short centromere on monocentric miniδ1-1. Transmission through the female was quite limited for all three ring minichromosomes (0–3.2%), whereas that through the male was relatively high (15.4–27.3%) compared with that of other supernumerary chromosomes in Arabidopsis. Ring structure without telomeres itself seems not to limit the female transmission.

Clinical and molecular studies in 15 females with ring X chromosomes: implications for r(X) formation and mental development

Abstract: We report clinical and molecular findings in 15 Japanese mosaic females with r(X) chromosomes, 45,X/46,X,r(X), confirmed by fluorescence in situ hybridization (FISH) analysis for DXZ1 and whole X chromosome painting. Cases 1-3, 5-7, and 11-13 had mental retardation (MR), the remaining cases being free from MR. FISH analysis showed that XIST was absent from the r(X) chromosomes in cases 1-4 and was present on the r(X) chromosomes in cases 5-15. X-inactivation analysis for the methylation status of the AR gene indicated that, of eight cases with XIST-positive r(X) chromosomes in more than 10% (23%-62%) of lymphocytes (cases 5-12), cases 5-10 had selective X-inactivation, whereas cases 11 and 12 had active X disomy. Microsatellite analysis for multiple loci on the pericentromeric region revealed that, of 11 cases with r(X) chromosomes in more than 10% (13%-62%) of lymphocytes (cases 1, 2, and 4-12), cases 1, 2, and 5-10 had heterozygous alleles for at least one locus, whereas cases 4, 11, and 12 had single alleles for all the loci examined. The results suggest that the r(X) and normal X chromosomes could be of biparental or uniparental origin, and that mental status in females with r(X) chromosomes is determined by multiple factors, including the presence or absence of XIST on the r(X) chromosomes and the size and frequency of active r(X) chromosomes, in addition to co-incidental genetic and environmental factors.

Flecked retina associated with café au lait spots, microcephaly, epilepsy, short stature, and ring 17 chromosome.

Abstract: Characteristic patterns of spots or flecks may occur in the ocular fundi of patients with heritable ocular and systemic diseases, including agerelated macular degeneration, pattern dystrophies, Stargardt's disease, fundus flavimaculatus, Bietti's crystalline tapetoretinal dystrophy, fundus albipunctatus, Alport's disease, primary hyperoxaluria, Sjogren-Larsson syndrome, and Gaucher's disease. We report herein a case of a striking pattern of retinal flecks in a patient with other congenital anomalies associated with ring 17 chromosome. Report of a Case. A 34-year-old man with multiple cafe au lait spots, seizures, a behavior disorder, microcephaly, short stature, and a ring 17 chromosome genotype had no ocular complaints. Visual acuity was 20/30 OU. There were a few cortical flecks in both lenses. The corneas and irides were normal and the vitreous was clear. Small, yellow-white flecks of variable size involving the level of the retinal pigment epithelium were scattered throughout the postequatorial fundi (Figure 1). There was a solitary,