Fragile X


Steven Strom of Raleigh, NC, writes to us about the Fragile X syndrome mentioned in this article:

Dear Editor,


As a parent of a child with Fragile X Syndrome, I wanted to clarify that Fragile X Syndrome is not a result of "chromosomal decay where one of the legs of the X has crumbled away" as described in the August 30th article by Tim Birdnow. 


According to the National Fragile X Foundation Website:  (

A change or mutation in a gene on the X chromosome causes the fragile X syndrome. Chromosomes are packages of genes that are passed from generation to generation. Most individuals have 46 chromosomes, two of which are sex chromosomes. In females, these are two X's; in males they are and X and Y. Genes are given names to identify them and the gene responsible for fragile X syndrome is called the FMR1 (fragile X mental retardation 1) gene. The mutation is in the DNA (the chemical that makes up genes), of the X chromosome.  The gene appears in three forms that are defined by the number of repeats of a pattern of DNA called CGG repeats. Individuals with less than 60 CGG repeats have a normal gene. Individuals with 60—200 CGG repeats have a premutation which means they carry an unstable mutation which can expand in future generations. Individuals with over 200 repeats have a full mutation which causes fragile X syndrome. The full mutation causes the gene to shut down or methylate a region of the FMR—1 gene. Normally, the FMR—1 gene produces an important protein called FMRP. When the gene is turned off, the individual does not make fragile X mental retardation protein (FMRP).  The lack of this specific protein causes fragile X syndrome.


Mr. Birdnow suggested that the gene decays.  That is not factual.  While we always appreciate the fact that more people are learning about Fragile X Syndrome, it's important to be armed with factual information about the cause and symptoms of Fragile X Syndrome.  I invite you to visit or for more information on Fragile X Syndrome.