What keeps the FMR1 gene from producing FMRP in Fragile X syndrome?
The information for making a protein has two parts: the introduction, and the instructions for the protein itself. Scientists call the introduction “the promoter region” of the gene because of its role in starting the protein-building process. (For a more complete description of how proteins are made and the parts of a cell involved in making a protein, see the Human cells 101 section.) The promoter region of the FMR1 gene contains repeats of a specific sequence (cytosine-guanine-guanine or CGG-see the Human cells 101 section for specific information about the CGG sequence) that, when normal, controls the activity level of the gene in building FMRP. The number of repeated sequences in the promoter region varies from person to person. Most people who do not have Fragile X have between six and 40 CGG repeats,3 with the average being about 30 repeats in the promoter region.4 However, in a mutated FMR1 gene, the promoter may have hundreds of repeated sequences. • A gene with 55 to 200 repe
