**Question:** The gene involved in the above condition is present on which chromosome?

A. 14
B. 5
C. 12
D. 17

**Core Concept:**
In this question, we are discussing a genetic disorder characterized by low platelet count, eosinophilia, and spontaneous bleeding, particularly nose bleeds and bloody diarrhea. This condition is associated with a defect in a specific gene leading to an impaired platelet function and increased eosinophilia. The correct explanation will focus on the involved gene, its function, and the clinical features associated with this genetic disorder.

**Why the Correct Answer is Right:**
The correct answer is **D. 17**. This is because the gene responsible for this condition, known as Factor V Leiden, is located on chromosome 17. Factor V Leiden is a genetic mutation in the F5 gene, which encodes the protein, Factor V. Factor V is an important component of the blood clotting cascade, specifically involved in the activation of Factor X during the clotting process. Factor V Leiden mutation leads to increased activity of Factor V, which results in a hypercoagulable state and increased risk of thromboembolic events like deep vein thrombosis and pulmonary embolism.

**Why Each Wrong Option is Incorrect:**

A. 14 (G6PD deficiency): This option refers to Glucose-6-Phosphate Dehydrogenase (G6PD) deficiency, which is located on chromosome X. G6PD deficiency is a genetic disorder affecting the red blood cells, causing hemolysis in response to certain drugs or infections. It is not related to bleeding disorders or platelet function.

B. 5 (Von Willebrand disease): Von Willebrand disease is a bleeding disorder caused by a deficiency or dysfunction in von Willebrand factor, located on chromosome 12. It is a hereditary platelet function disorder, distinct from Factor V Leiden, as it affects platelet function and bleeding tendency but does not lead to thrombotic events.

C. 12 (Hemophilia A): Hemophilia A is a bleeding disorder caused by a deficiency in Factor VIII, located on chromosome X. It affects platelet function and clotting factors, leading to severe bleeding tendencies, but is not related to Factor V or thrombotic events.

D. 17 (Factor V Leiden): As explained above, Factor V Leiden is a genetic mutation on chromosome 17, causing a hypercoagulable state and thrombotic events, which is the correct answer.

**Clinical Pearl:**

Understanding the genetics and pathophysiology of Factor V Leiden is essential for medical professionals, particularly haematologists, to diagnose and manage patients with this genetic disorder. It is critical to differentiate it from other bleeding disorders like von Willebrand disease, hemophilia A, and G6PD deficiency, which have distinct clinical features and genetic locations.

**Why to Memorize:**

Factor V Leiden is an essential concept for medical students and physicians to recognize the clinical presentation of this genetic disorder, which can be mistaken for other bleeding disorders due to overlapping symptoms and signs. Familiarizing