Fragile X Syndrome

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  • Topic: DNA, Mental retardation, Fragile X syndrome
  • Pages : 3 (1024 words )
  • Download(s) : 389
  • Published : May 7, 2009
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Fragile X syndrome, also called Martin-Bell syndrome, is a syndrome of X-linked mental retardation. In 1943, Martine and Bell described a pedigree of X-linked mental disability. Chris and Weesam were first to sight an unusual “maker X chromosome” with mental disability in 1969. It is also the most common known cause of autism. Autism is a brain development disorder that impairs social interaction and communication. It can also cause restricted and repetitive behavior. It all starts before a child is three years old. It affects about 1 in 4000 males and 1 in 8000 females. It can cause a range of mental impairment, varying from mild to severe, and can also cause many other typical features and symptoms.

The cause of fragile X syndrome is by mutation of a gene on the X- chromosome. The gene makes a protein needed for brain development, but the mutation causes a person to make less or none of the protein, which cause fragile X syndrome. That gene is called FMR1. FMR1 stands for fragile X mental retardation 1, which is a human gene that provides instructions to make a protein. The gene can be passed silently without any symptoms showing for generation before a child is affected by fragile X syndrome. Fragile X syndrome is inherited, mothers may be a carrier of the mutation and pass it on to their children or may have a pre-mutation that expands to a full mutation when passes on to the next generation. Girls have another X-chromosome, which usually does not have the mutation and can partially compensate for the nonfunctioning one. Therefore, boys are affected more than girls are because boys have only one X chromosome.

Physical characteristic s and behaviors portrays the symptoms of fragile X syndrome. Large or protruding ears and forehead, elongated face, large head, flexible finger joints, high palate, and flat feet are the physical characteristics. In addition, during a boy’s puberty, they usually develop large testicles and...
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