**Question:** True about fragile-X syndrome

A. It is a genetic disorder caused by a mutation in the FMR1 gene.
B. It primarily affects males and results in intellectual disability.
C. It is caused by a deletion in the X chromosome.
D. It can be treated with medications targeting the FMR1 gene mutation.

**Correct Answer: D. It can be treated with medications targeting the FMR1 gene mutation.**

**Core Concept:** Fragile-X syndrome is a genetic disorder characterized by intellectual disability, behavioral problems, and physical features. It is primarily caused by a mutation in the FMR1 gene, which leads to the absence or reduced expression of the FMRP protein.

**Why the Correct Answer is Right:** Fragile-X syndrome results from a mutation in the FMR1 gene, leading to the absence of the FMRP protein. This protein plays a crucial role in synaptic plasticity, which is essential for normal cognitive function. As a result, individuals with fragile-X syndrome have impaired synaptic plasticity, leading to intellectual disability and other cognitive and behavioral issues.

**Why Each Wrong Option is Incorrect:**

A. Deletions in the X chromosome are responsible for Turner's syndrome, not fragile-X syndrome. Fragile-X syndrome is caused by mutations in the FMR1 gene.

B. Fragile-X syndrome primarily affects males, but both genders can be affected. It is not exclusively a condition affecting males.

C. Fragile-X syndrome is caused by a mutation in the FMR1 gene, not by deletions in the X chromosome.

**Clinical Pearl:** Identifying the cause of intellectual disability is essential for appropriate management and counseling of affected individuals and their families. While there is no cure for fragile-X syndrome, medications like risperidone and mitoxantrone have been found to improve some symptoms, such as hyperactivity and seizures, in some individuals with fragile-X syndrome. However, the treatment options are limited, and further research is needed to develop targeted therapies for this condition.