Fragile X syndrome and its associated conditions are caused by mutations, or changes, in the FMR1 gene. The mutation affects how the body can use the gene to make the Fragile X mental retardation protein, or FMRP.
On a gene, the information for making a protein has two parts: the introduction and the instructions for making the protein itself. Researchers call the introduction the promoter because of how it helps start the process of building the protein.
The promoter part of the FMR1 gene normally includes many repeats—repeated instances of a trio of DNA bases called a triplet repeat—in this case, many copies of the CGG triplet repeat—to help build the protein.
The number of repeats in the promoter varies from person to person.
Premutations and full mutations in the promoter region of the FMR1 gene can have different effects.
Premutations can cause specific disorders taht aren't found in people with the full mutation:
The number of repeats in the promoter region also affects the severity of a person’s symptoms of Fragile X syndrome:
Parents who have a FMR1 premutation may have no symptoms but still pass along the premutation to their children. That means their children could have Fragile X-associated disorders, including FXPOI. Also, the premutation can expand when it's passed along, so that a child of a parent with a premutation could have Fragile X syndrome.
All related topics
All related news