Ring chromosome
From Wikipedia, the free encyclopedia
A ring chromosome is a chromosome whose arms have fused together to form a ring. A ring chromosome is denoted by the symbol r. Ring chromosomes may form in cells following genetic damage by mutagens like radiation, they may also arise spontaneously during development.
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[edit] Formation
Normally, the ends of a chromosome are lost, enabling the arms to fuse together. However, ring formation can also occur with only one end being lost. In rare cases, the telomeres at the ends of a chromosome fuses without any disappearing of material.[1]
[edit] Associated diseases
Human genetic disorders can be caused by spontaneous ring chromosome formation; although ring chromosomes are very rare, they have been found in all human chromosomes. Disorders arising from the formation of a ring chromosome include ring chromosome 20 syndrome where a ring formed by one copy of chromosome 20 is associated with epilepsy; ring chromosome 14 and ring chromosome 13 syndrome are associated with mental retardation and dysmorphic facial features; ring chromosome 15 is associated with mental retardation, dwarfism and microcephaly. Ring formation of an X-chromosome causes Turner syndrome.
[edit] See also
[edit] References
- Schmidt et al. 1981. Ring chromosome 14: a distinct clinical entity. Journal of Medical Genetics 18:304-307
[edit] References
- ^ Mitotic and meiotic behaviour of a naturally transmitted ring Y chromosome: reproductive risk evaluation Núria Arnedo, Carme Nogués, Mercè Bosch and Cristina Templado
[edit] External links
- Atlas of Genetics and Cytogenetics in Oncology and Haematology, explains HOW the ring formation causes abnormalities.
