Which genetic condition is characterized by a mutation in the FMR1 gene and leads to intellectual disability?

Fragile X Syndrome is a genetic condition caused by a mutation in the FMR1 gene located on the X chromosome. This mutation typically involves an expansion of a CGG repeat sequence that affects the production of the fragile X mental retardation protein (FMRP), which is crucial for normal brain development and function.

Individuals with Fragile X Syndrome often exhibit intellectual disabilities, which can range from mild to moderate or severe, along with behavioral issues, social anxiety, and other characteristics, such as physical features that may include an elongated face or large ears. This condition is the most common inherited cause of intellectual disability and can manifest in both males and females, although males are usually more severely affected due to having only one X chromosome.

On the other hand, conditions like Down Syndrome, Turner Syndrome, and Williams Syndrome are associated with different genetic causes. Down Syndrome typically results from an extra chromosome 21, Turner Syndrome arises from the absence of part or all of a second sex chromosome, and Williams Syndrome is associated with a deletion of genetic material from chromosome 7. Each of these conditions has distinct features and causes that differentiate them from Fragile X Syndrome.