Definitions for fragile x syndrome
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fragile X syndrome(Noun)
A particular, genetic syndrome, caused by the excessive repetition of a particular trinucleotide.
Fragile X syndrome
Fragile X syndrome, Martin–Bell syndrome, or Escalante's syndrome, is a genetic syndrome that is the most widespread single-gene cause of autism and inherited cause of mental retardation among boys. It results in a spectrum of intellectual disabilities ranging from mild to severe as well as physical characteristics such as an elongated face, large or protruding ears, and large testes, and behavioral characteristics such as stereotypic movements, and social anxiety. Fragile X syndrome is associated with the expansion of the CGG trinucleotide repeat affecting the Fragile X mental retardation 1 gene on the X chromosome, resulting in a failure to express the fragile X mental retardation protein, which is required for normal neural development. Depending on the length of the CGG repeat, an allele may be classified as normal, a premutation, or full mutation. A definitive diagnosis of fragile X syndrome is made through genetic testing to determine the number of CGG repeats. Testing for premutation carriers can also be carried out to allow for genetic counseling. The first complete DNA sequence of the repeat expansion in someone with the full mutation was generated by scientists in 2012 using SMRT sequencing.
U.S. National Library of Medicine
Fragile X Syndrome
A condition characterized genotypically by mutation of the distal end of the long arm of the X chromosome (at gene loci FRAXA or FRAXE) and phenotypically by cognitive impairment, hyperactivity, SEIZURES, language delay, and enlargement of the ears, head, and testes. MENTAL RETARDATION occurs in nearly all males and roughly 50% of females with the full mutation of FRAXA. (From Menkes, Textbook of Child Neurology, 5th ed, p226)
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"fragile x syndrome." Definitions.net. STANDS4 LLC, 2015. Web. 1 Dec. 2015. <http://www.definitions.net/definition/fragile x syndrome>.