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![[-- Fragile X syndrome --]](Images/Terms/FragileX.gif)
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| defined: |
After Down syndrome, the second most frequent genetic cause of mental retardation. The disorder is one of a group of diseases that results from an unusual kind of mutation: a repeating sequence of three letters of the DNA code, called a triplet repeat or trinucleotide repeat. In Fragile X, the repeating triplet is CGG, cytosine-guanine-guanine, in a gene on the X chromosome. The larger the number of repeats they possess, the more likely patients are to be seriously impaired. People who possess just a few repeats are carriers but often not affected.
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| explained: |
Listen to a detailed explanation.
Dr. Robert Nussbaum, of the National Human Genome Research Institute's Laboratory of Genetic Disease Research, defines Fragile X syndrome. |
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related terms: |
cell, chromosome, gene, nucleotide, sex chromosome | |
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