A 22-year-old college wrestler comes for a sports physical examination. He tells you that he often feels excessively short of breath during practice and even has had chest pain that resolves with rest. He reports experiencing a syncopal episode 3 months ago while running a marathon. While taking the family history he tells you that his father died of ‘earlier-than-normal age’ sudden death. You send the patient for an echocardiogram, which reveals a hypertrophic heart, a thickened interventricular septum and a functional left ventricular outflow obstruction durings systole. Of the following, which is the most common gene mutation found in this disorder?
