Causes of Fragile X Syndrome

Loss or deficiency of FMR1 protein disrupts nervous system functioning and causes signs and symptoms of fragile X syndrome.

What causes Fragile X Syndrome?

Fragile X Syndrome is an inherited disorder resulting from a mutation in FMR1 (Fragile X Mental Retardation 1) gene located on X-chromosome. FMR1 gene is necessary for making a protein called FMRP (fragile X mental retardation1 protein), which is important for nerve function.

Some people have full mutation of the gene and show characteristic features of the condition. Others may show some changes in the gene, but the change may not be significant enough to produce visible features. These individuals are said to have a premutation. A person with a premutation can transmit the condition to his/her offspring without suffering from the condition.

Fragile X Syndrome DNA

Men have only one X chromosome, which they pass on to their daughter. Thus, if a male with the premutation has a son, the son will not inherit this defect from his father. However, since the father passes the X-chromosome to his daughter (the other X-chromosome will come from the mother), the daughter may have the premutation in her genes but again, will not suffer from the condition. However, there is a good chance that her child may suffer from the condition.


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