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.

Ring chromosome 14 and immunoglobulin locus

Abstract: A 2.5-yr-old girl was evaluated for seizurelike episodes and psychomotor and growth retardation. Cytogenetic study showed a ring 14 chromosome in most cells, with some cells having monosomy 14. Rarely, a cell showed a double ring chromosome 14. Both parents had normal chromosomes. Because serum immunoglobulins have been mapped to the distal portion of 14q, we attempted to correlate Ig levels with the deletion involved in the formation of this ring. No decrease in IgG, IgM, IgA, IgE, and IgD serum levels was observed. The normal serum Ig levels found in the proposita are compatible with the suggestion that the Ig loci are not located on the terminal portion of 14q but more proximally in band 14q32. However, because Gm and Am allotyping was not available mapping was not conclusive.

Supernumerary Ring Chromosome: An Etiology for Pallister-Killian Syndrome?

Abstract: Characterization of marker chromosomes before the introduction of array CGH (aCGH) assays was only based on their banding patterns (G, C, and NOR staining) and fluorescent in situ hybridization techniques. The use of aCGH greatly improves the identification of marker chromosomes in some cases. We describe an atypical case of Pallister-Killian syndrome (PKS) detected at prenatal diagnosis with a very unusual cytogenetic presentation: a supernumerary ring chromosome including two copies of 12p. A similar anomaly described in a postnatal patient suggests ring chromosome as a possible cause of PKS. Extra ring chromosomes might be a more common etiology for PKS than previously thought, given the difficulty in their characterization before the advent of aCGH.

Endocrine and cytogenetic studies in a patient with Turner's phenotype and a ring chromosome.

Abstract: A 27-year-old woman with secondary amenorrhea and some of the somatic stigmata of Turner′s syndrome was found to have a ring chromosome. Laparoscopy and ovarian biopsy showed hypoplastic ovaries and an absence of primordial follicles. Endocrine evaluation showed a normal 24-h mean LH level (12.5 mlU/ml), an elevated FSH level (28 mlU/ml) and a normal plasma estradiol level (64 pg/ml). The augmented FSH and normal LH response to LH-RH is similar to what is found in men with germinal cell aplasia (Sertoli-cell only). The synchronous initiation of normal LH and abnormally augmented FSH secretory episodes in this patient suggests the absence or decrease of some factor normally produced by the ovarian follicle which modulates the release of FSH in response to LH-RH.

Gray Matter Heterotopia, Mental Retardation, Developmental Delay, Microcephaly, and Facial Dysmorphisms in a Boy with Ring Chromosome 6: A 10-Year Follow-Up and Literature Review.

Abstract: Ring chromosome 6, r(6), is an extremely rare cytogenetic abnormality with clinical heterogeneity which arises typically de novo. The phenotypes of r(6) can be highly variable, ranging from almost normal to severe malformations and neurological defects. Up to now, only 33 cases have been reported in the literature. In this 10-year follow-up study, we report a case presenting distinctive facial features, severe developmental delay, and gray matter heterotopia with r(6) and terminal deletions of 6p25.3 (115426-384174, 268 kb) and 6q26-27 (168697778-170732033, 2.03 Mb) encompassing 2 and 15 candidate genes, respectively, which were detected using G-banding karyotyping, FISH, and chromosomal microarray analysis. We also analyzed the available information on the clinical features of the reported r(6) cases in order to provide more valuable information on genotype-phenotype correlations. To the best of our knowledge, this is the first report of gray matter heterotopia manifested in a patient with r(6) in China, and the deletions of 6p and 6q in our case are the smallest with the precise size of euchromatic material loss currently known.

Chromosome chromatid rearrangements resulting from the mitotic crossing-over between sister-chromatids in ring chromosomes of Creptis capillaris.

Abstract: All radiation-induced aberrations in dry seeds of Crepis capillaris are chromosome rearrangements. The main types of chromosome rearrangements in the above tests were asymmetrical and symmetrical exchanges, ring chromosomes and ring deletions. The majority of ring chromosomes is of a chromosomes type which brings about paired rings. Fig. 1 presents the mechanism of the production of the paired rings. In a number of cases the structure of rings proved to be quite unexpected. Among middle size rings single rings proved to occur in 18.8%, among microrings-1.9% cases. Somewhat fewer are presented by pairs of rings one inside the other. The large rings present complex figures made by tangled chromatids. Two rings make one due to mitotic crossing-over between sister-chromatids (Fig. 5). Double crossing-over would lead to the exchange of part of material between two independent rings or to one ring being thrust into the other due to different strand positions in two points of the exchange. Large rings is the provision of complicated exchanges.