## **Core Concept**
The question tests understanding of a specific genetic disorder leading to a hypercoagulable state, which is characterized by an increased tendency to form blood clots. This condition arises due to mutations in specific genes that encode for proteins involved in the coagulation cascade. Factor V is a crucial protein in this pathway.

## **Why the Correct Answer is Right**
The correct answer, **Factor V Leiden**, is a variant of the factor V gene. This mutation leads to a change in the factor V protein, making it resistant to inactivation by activated protein C (APC). Normally, APC regulates the coagulation cascade by inactivating factors Va and VIIIa. The mutation in factor V Leiden results in a loss of this regulatory control, leading to an increased propensity for thrombosis. This condition is a well-known cause of hereditary thrombophilia.

## **Why Each Wrong Option is Incorrect**
- **Option A:** While there are multiple genetic conditions that can lead to a hypercoagulable state, the question specifically mentions a defective factor V gene. Therefore, any option not directly related to factor V would be incorrect.
- **Option B:** This option is not specified, but based on the context, any condition not directly linked to a factor V gene defect would not apply.
- **Option C:** Similarly, without specifics, any option not directly tied to a factor V mutation leading to hypercoagulability would be incorrect.
- **Option D:** Given that the correct answer is related to factor V Leiden, any other option would be incorrect if it does not describe this condition.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that **Factor V Leiden** is the most common inherited thrombophilic condition. It is particularly relevant in the context of venous thromboembolism (VTE), and testing for this mutation may be considered in patients with a personal or family history of VTE, especially if it occurred at a young age or in the absence of clear risk factors.

## **Correct Answer:** . Factor V Leiden