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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.


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Journal ArticleDOI
TL;DR: The causes of B9 loss in the endosperm and the sporophyte were investigated and it is suggested that the isochromosome is a by-product of telocentric formation at the second pollen mitosis, and does not arise directly from the B9 chromosome.
Abstract: The B 9 chromosome of maize exhibits a very ordered type of instability at the second pollen mitosis, when nondisjunction may reach a level of 95%. Much less commonly the chromosome is unstable during early development of the kernel. Instability in the kernel produces recessive sectors in either the endosperm or the sporophyte, reflecting the absence of dominant markers carried by the B 9. The causes of B 9 loss in the endosperm and the sporophyte were investigated for the two observable classes of sectoring: fractional loss (single event) and multiple loss (mosaic pattern). The fractional class represents isochromosome formation by the B 9 (Carlson, 1970, 1971). Data presented here suggest that the isochromosome is a by-product of telocentric formation at the second pollen mitosis, and does not arise directly from the B 9 chromosome. The chromosomal basis for the mosaic pattern of B 9 loss is not completely known. However, one class of mosaic kernels displays a heritable instability of the B 9 chromosome which apparently results from ring chromosome formation by the B 9. The time of origin of the ring B 9 chromosome is prior to the second pollen mitosis, since the unstable chromosome generated in the male parent is transmitted to both the endosperm and the sporophyte. Finally, a genetic factor controlling B 9 stability in the developing endosperm has been found. A single plant (1818-1), crossed as a female parent to a B 9-containing stock, induced a mosaic pattern of B 9 loss in the endosperm at a very high rate. The characteristics of this plant are being investigated.

15 citations

Journal ArticleDOI
TL;DR: A case of triple mosaicism involving chromosome 18 is described in a girl with abnormal skin pigmentation similar to hypomelanosis of Ito, illustrating a non-random association of chromosomal mosaicism with abnormalskin pigmentation.
Abstract: A case of triple mosaicism involving chromosome 18 is described in a girl with abnormal skin pigmentation similar to hypomelanosis of Ito. The karyotype is 46,XX, -18, + del(18)(p11.23-->pter)/46,XX, -18, + idic(18)(p11.23)/46,XX, -18, + r(18). The patient displays some clinical features of monosomy 18p and a few signs of trisomy 18q. Our case illustrates a non-random association of chromosomal mosaicism with abnormal skin pigmentation.

15 citations

Journal ArticleDOI
TL;DR: Cytogenetic analysis by Q banding demonstrated minimal chromosome deletion and the karyotype was considered to be 46,XY,r(11) (p15q25) and high resolution G banding showed no visible loss of chromatin.
Abstract: Two cases of ring chromosome 11 are reported. Both had mental retardation, microcephaly, and short stature. High resolution G banding in case 1 showed no visible loss of chromatin, the karyotype being assessed as 46,XX,r(11) (p15 X 4q2 X 5). In case 2, a Wilm's tumour developed at 8 months and the child died at 18 months. Cytogenetic analysis by Q banding demonstrated minimal chromosome deletion and the karyotype was considered to be 46,XY,r(11) (p15q25).

15 citations

Journal ArticleDOI
TL;DR: A 15-month-old boy with mild developmental delay and several minor anomalies was found to be mosaic 46,XY/47,XY,+mar(1), where mar(1) was a small de novo ring identified by FISH with a painting type DNA probe.
Abstract: A 15-month-old boy with mild developmental delay and several minor anomalies was found to be mosaic 46,XY/47,XY ,+mar(1). The marker r(1) was a small de novo ring identified by FISH with a painting type DNA probe.

15 citations

Journal ArticleDOI
TL;DR: In women with isolated gonadal dysgenesis but otherwise normal stature, the testis determining factor or SRY gene may have been removed from the Y chromosome or may be mutated as discussed by the authors.
Abstract: Although specifically male, the human Y chromosome may be observed in female karyotypes, mostly in women with Turner syndrome stigmata. In women with isolated gonadal dysgenesis but otherwise normal stature, the testis determining factor or SRY gene may have been removed from the Y chromosome or may be mutated. In other women with Turner syndrome, the karyotype is usually abnormal and shows a frequent 45,X/46,XY mosaicism. In these cases, the phenotype depends on the ratio between Y positive and 45,X cell lines in the body. When in mosaicism, Y chromosomes are likely to carry structural abnormalities which explain mitotic instability, such as the existence of two centromeres. Dicentric Y isochromosomes for the short arm (idic[Yp]) or ring Y chromosomes (r[Y]) are the most frequent abnormal Y chromosomes found in infertile patients and in Turner syndrome in mosaic with 45,X cells. Although monocentric, deleted Y chromosomes for the long arm and those carrying microdeletions in the AZF region are also instable and are frequently associated with a 45,X cell line. Management of infertile patients carrying such abnormal Y chromosomes must take into account the risk and the consequences of a mosaicism in the offspring.

15 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202310
202221
202123
202019
201919
201836