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.

Interstitial deletion and ring chromosome derived from 16q.

Abstract: An interstitial deletion of 16q was identified in an infant with failure to thrive, dysmorphic facies, and congenital heart defects. The mother of this infant had a similar deletion of 16q with ring formation of a fragment presumed to be derived from the deleted portion of 16q. We discuss these cases and compare them to other reports of 16q deletions.

Constitutional ring chromosomes and tumour suppressor genes.

Abstract: The types of malignancy reported in carriers of constitutional ring chromosomes r(11), r(13), and r(22) are concordant with the chromosomal assignment of tumour suppressor loci associated with Wilms' tumour, retinoblastoma, and meningioma It is suggested that the somatic instability of ring chromosomes may play a role in this association and that constitutional ring chromosomes may be a source for mapping of tumour suppressor loci with the potential for covering most or all of the human genome The hypothesis predicts the presence of a locus on chromosome 10 associated with follicular carcinoma of the thyroid, in line with previous cytogenetic findings of rearrangements involving chromosome 10 in thyroid tumours, and a locus on chromosome 22 associated with testicular cancer Development of neurofibromatoses (NF) that do not fulfil the clinical criteria of neurofibromatosis type 2 (NF2) in carriers with r(22) suggests either the presence of an additional NF locus on chromosome 22 or that ring chromosome mediated predisposition to somatic mutation of a specific tumour suppressor may be associated with atypical development of features usually associated with germline mutations

The three-dimensional organization of polytene nuclei in male Drosophila melanogaster with compound XY or ring X chromosomes.

Abstract: The three-dimensional organization of polytene chromosomes within nuclei containing rearranged X chromosomes was examined in male Drosophila melanogaster. Salivary glands of third instar larvae containing either an inverted X chromosome (YSX.YL, In(1)EN/O) or a ring X chromosome (R(1) 2/BSYy+) were fixed, embedded, and serially sectioned. The nuclei in contiguous groups of cells were modeled and analyzed. We find that for both genotypes the three-dimensional behavior at each euchromatic locus is independent of the orientation of the chromosome on which it resides, independent of the behavior of loci not closely linked to it, and not similar in neighboring cells. The preference for right-handed chromosome coiling noted in previous studies is shown to be independent of homologous pairing. However, a relation between the extent of chromosome curvature and the handedness of chromosome coiling is present only in homologously paired chromosomes. The attached-XY chromosome has two previously undescribed behaviors: a nearly invariant association of the euchromatic side of the proximal heterochromatin/euchromatin junction with the nucleolus and a frequent failure of this site to attach to the chromocenter. The relative chromosome arm positions are often similar in several neighboring cells. The size of these patches of cells, assuming that they represent clones, indicates that such arrangements are at best quasi-stable: they may be maintained over at least one, but less than four, cell divisions. The observed nuclear organization in salivary glands is inconsistent with the idea that position in the polytene nucleus plays a major role in the normal genetic regulation of euchromatic loci.

Two new cases of analphoid marker chromosomes.

Abstract: Supernumerary marker chromosomes (SMCs) without detectable alphoid DNA represent a rare and interesting class of rearranged marker chromosomes. These SMCs are predicted to have a neocentromere and have been referred to as neocentric marker chromosomes (NMCs). We report the molecular cytogenetic characterization of two new cases of neocentromere-containing chromosomes, one on 1q43∼44 and one on 15q26. Both cases were examined using fluorescence in situ hybridization (FISH) with various alpha-satellite DNA probes, and no alphoid DNA was detected. In case 1, the NMC originated from the distal long arm of chromosome 1 by chromosomal microdissection and reverse painting. This marker lacked detectable chromosome 1q subtelomeric sequences, and therefore appeared to be a small ring chromosome. After genetic counseling with a high risk for a MCA/MR syndrome (trisomy 1q43 q44), the family continued the pregnancy. At age 6 months, the infant demonstrated no congenital or developmental anomalies. This is the first published example of a NMC derived from chromosome 1q. The marker may be one of the smallest, if not the smallest, human NMC reported to date. In case 2, fetal ultrasonography indicated a complex heart defect (abnormal return of lower vena cava, atrial septum malformation) and bilateral hydronephrosis. Molecular cytogenetic analysis showed an inverted duplication of the distal long arm of chromosome 15 (tetrasomy 15q24 qter). The pregnancy was terminated. Autopsy demonstrated polycystic left kidney and dysplastic right kidney. Case 2 represents the ninth report of a neocentromere on distal chromosome 15q, suggesting that this region may possibly especially support the formation of neocentromeres. © 2002 Wiley-Liss, Inc.

A child with a group-G ring chromosome

Abstract: Clinical, cytogenetic and blood-grouping studies are reported in a child, who was found to have a stable group-G ring chromosome. Difficulties in the detection of ring formation in chromosomes of the G-group have been discussed. No gene losses due to the ring formation could be detected.