What genetic condition is characterized by increased CGG repeat and associated with intellectual disabilities?

Fragile X syndrome is a genetic condition that results from an expanded repetition of the CGG trinucleotide sequence within the FMR1 gene located on the X chromosome. This mutation leads to a reduction or absence of the fragile X mental retardation protein (FMRP), which is crucial for normal neural development. The increase in CGG repeats can lead to varying degrees of intellectual disabilities, making it the most common inherited cause of intellectual disability in males.

In addition to intellectual disability, individuals with Fragile X syndrome may exhibit a range of behavioral, physical, and emotional characteristics, including developmental delays, anxiety, and autistic behavior. The condition is hereditary and often seen in families, with women typically being carriers and having a lower risk of severe intellectual disability compared to males.

Other conditions listed do not have the same genetic mechanism connected to CGG repeat expansion. Down syndrome is primarily described by the presence of an extra chromosome 21, Turner syndrome is a condition where there is a complete or partial absence of one X chromosome in females, and Williams syndrome is due to a deletion of a segment of chromosome 7 and has distinct cardiovascular and developmental features.