True about Fragile X syndrome is-
**Core Concept**
Fragile X syndrome is a genetic disorder caused by an expansion of the **CGG repeat** in the **FMR1 gene**, leading to **X-linked dominant** inheritance. This results in a deficiency of the **fragile X mental retardation protein (FMRP)**, which is essential for normal brain development. The syndrome is characterized by intellectual disability, behavioral problems, and distinct physical features.
**Why the Correct Answer is Right**
Although the specific correct answer option is not provided, the correct answer would relate to the genetic or clinical aspects of Fragile X syndrome, such as its inheritance pattern, the role of **FMR1 gene** mutations, or its clinical manifestations, including intellectual disability, **macroorchidism** in males, and characteristic facial features.
**Why Each Wrong Option is Incorrect**
**Option A:** Would be incorrect if it suggested an autosomal recessive inheritance pattern, as Fragile X syndrome is **X-linked dominant**.
**Option B:** Might be incorrect if it described the syndrome as being caused by a point mutation rather than an **expansion of CGG repeats**.
**Option C:** Could be wrong if it stated that the syndrome primarily affects females, as it more severely affects males due to their having only one X chromosome.
**Option D:** Would be incorrect if it implied that the syndrome does not involve intellectual disability, as this is a hallmark feature.
**Clinical Pearl / High-Yield Fact**
A key point to remember is that Fragile X syndrome is the most common cause of inherited intellectual disability and the most common known genetic cause of **autism** or autism spectrum disorders.
**Correct Answer:**