scispace - formally typeset
Search or ask a question
Topic

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.


Papers
More filters
Journal ArticleDOI
TL;DR: This work reports on 2 prenatal diagnosis cases, where a ring was noted in 25 and 60% of the amniocytes, respectively, and the large amount of C-band positive material on the extra chromosome and the normal level 2 fetal ultrasound examination suggested a favorable outcome in both cases, but the possibility of mental retardation could not be ruled out.
Abstract: De novo supernumerary small ring chromosomes have mainly been reported in pediatric patients with clinical abnormalities, thus, there may be bias of ascertainment. Reports on prenatally diagnosed cases with postnatal follow-up are rare. With the availability of chromosome specific alpha-satellite centromeric probes, the interest in these previously unidentifiable supernumerary small ring chromosomes has been rekindled [Callen et al.: J Med Genet 27: 155-159, 1990; Callen et al.: Am J Hum Genet 48:769-782, 1991; Callen et al.: Am J Med Genet 43:709-715, 1992]. We report on 2 prenatal diagnosis cases, where a ring was noted in 25 and 60% of the amniocytes, respectively. The initial G- and C-banding in Case 1 allowed an assumption of a chromosome 1 origin of the extra chromosome. This was confirmed by fluorescence in situ hybridization (FISH) studies using the appropriate probes. No similar initial assumption could be made in Case 2; thus, random trials with multiple probes were performed. A chromosome 19 origin in Case 2 was eventually concluded. The large amount of C-band positive material on the extra chromosome and the normal level 2 fetal ultrasound examination suggested a favorable outcome in both cases, but the possibility of mental retardation could not be ruled out. An empiric risk figure with regard to prenatally diagnosed de novo supernumerary small ring chromosomes is not available. Although the decision making processes of the parents were different, they both decided to continue the pregnancy. At age 9 months and 1 1/2 years both children, a girl and a boy, showed normal growth and development.

36 citations

Journal ArticleDOI
TL;DR: McClintock et al. as discussed by the authors described the breakage-fusion-bridge cycle, a model for a repeating pattern of chromosome behavior that is triggered by an initial breakage.
Abstract: When Barbara McClintock irradiated strains of Indian corn in the early 30s, she identified ring chromosomes, which she soon realized were a special case of chromosomes broken by radiation; the broken ends sometimes fused to one another and formed a ring (1, 2). This discovery led McClintock to hypothesize the existence of a special structure at the chromosome tip that would maintain chromosome stability. In 1941 she described the breakage-fusion-bridge cycle, a model for a repeating pattern of chromosome behavior that is triggered by an initial breakage (3). Normally, each chromatid strand has one centromere, and the chromosome ends remain capped by the telomeres that protect the ends from sticking to one another. But sometimes, harmful substances or radiation damage a chromatid and cause it to break. Without telomere caps, the new ends stick to each other, and the resulting fused chromosome has two centromeres as well as a duplication of some of the genes from that chromosome. When cell division occurs, the two centromeres of this unusual chromosome may be pulled to the opposite spindle poles of the cell, forming an irregular, long chromosome bridge between the two newly forming daughter cells (Fig. 1 A and B). Eventually, the abnormal chromatid breaks in two or may be left behind during cell division. If the chromosome ends are broken, they are likely to rejoin again, reforming a chromosome bridge at the next division.

36 citations

Journal ArticleDOI
TL;DR: Cytogenetic analysis of a 15 month old girl evaluated for severe developmental delay and acral skeletal hypoplasia revealed a predominant 46,XX,r(15) karyotype, and Cellular mosaicism for chromosome 15 aneuploidy most likely accounts for the patient's phenotypic abnormalities.
Abstract: Cytogenetic analysis of a 15 month old girl evaluated for severe developmental delay and acral skeletal hypoplasia revealed a predominant 46, XX, r(15) karyotype. Prophase banding analysis showed minimal deletion of the ring chromosome (breakpoints pl2 and q26), while silver staining showed it to have an active nucleolus organizing region, multiple abnormal secondary configurations, and decreased satellite association. Although there was no spontaneous instability in the rest of the karyotype, gentian violet-induced chromosome breakage was significantly increased. The rate of spontaneous sister chromatid exchange was not elevated. Cellular mosaicism for chromosome 15 aneuploidy most likely accounts for the patient’s phenotypic abnormalities.

36 citations

Journal ArticleDOI
TL;DR: Ring chromosomes are circular DNA molecules, which occur rarely in eukaryotic nuclear genomes, and potential clinical applications of artificially created RCs for large-scale chromosome rearrangement treatment are examined.
Abstract: Ring chromosomes (RCs) are circular DNA molecules, which occur rarely in eukaryotic nuclear genomes. Lilian Vaughan Morgan first described them in the fruit fly. Human embryos very seldom have RCs, about 1:50,000. Carriers of RCs may have varying degrees of symptoms, from healthy phenotype to serious pathologies in physical and intellectual development. Many authors describe common symptoms of RC presence: short stature and some developmental delay that could be described as a “ring chromosome syndrome.” As a rule, RCs arise de novo through the end-joining of two DNA double-strand breaks, telomere-subtelomere junction, or inv dup del rearrangement in both meiosis and mitosis. There are family cases of RC inheritance. The presence of RCs causes numerous secondary chromosome rearrangements in vivo and in vitro. RCs can change their size, become lost, or increase their copy number and cause additional deletions, duplication, and translocations, affecting both RCs and other chromosomes. In this review, we examine RC inheritance, instability, mechanisms of formation, and potential clinical applications of artificially created RCs for large-scale chromosome rearrangement treatment.

36 citations

Journal ArticleDOI
TL;DR: It is deduced that retinal abnormalities and epilepsy map within the proximal 14q11.2- q12 region, because this region is preserved in all patients with ring 14, and it is speculated that genes residing in the proximate 14q interval are disregulated through heterochromatinization spreading from the adjacent short arm of the chromosome.

36 citations


Network Information
Related Topics (5)
Missense mutation
18.5K papers, 806.1K citations
83% related
Chromosome
17.5K papers, 660K citations
82% related
Gene mutation
41.4K papers, 1.3M citations
80% related
Germline mutation
14.4K papers, 799.6K citations
80% related
Mutation
45.2K papers, 2.6M citations
79% related
Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202310
202221
202123
202019
201919
201836