## **Core Concept**
Marital skew refers to a phenomenon where certain genetic conditions are more likely to be passed down through one parental lineage due to the age of the parents at the time of conception. This concept is particularly relevant in the context of genetic disorders that exhibit parental age effects.

## **Why the Correct Answer is Right**
The correct answer, **Fragile X syndrome**, is associated with a marital skew, particularly a paternal age effect, but more accurately, it's related to the expansion of CGG repeats in the FMR1 gene. However, the anticipation and parental age effect seen in some genetic disorders can sometimes be confused with marital skew. Fragile X syndrome is primarily caused by an expansion of CGG repeats in the FMR1 gene on the X chromosome, leading to its silencing and the absence of the FMRP protein. The phenomenon of marital skew can influence the risk of certain genetic conditions but is most directly related to disorders caused by mutations or expansions that have a parental origin.

## **Why Each Wrong Option is Incorrect**
- **Option A:** Not provided, so we cannot assess.
- **Option B:** Not provided, so we cannot assess.
- **Option D:** Not provided, so we cannot assess.

## **Clinical Pearl / High-Yield Fact**
A key clinical pearl related to Fragile X syndrome is that it is the most common cause of inherited intellectual disability. The syndrome is characterized by physical features such as a long face, large or protruding ears, and, in males, macroorchidism post-puberty. Early diagnosis and intervention are crucial for managing the associated developmental delays and behavioral issues.

## **Correct Answer:** C. Fragile X syndrome.