Mutations in the Notch1 gene are associated with diseases such as aortic valve disease, type 1 (AOVD1), Adams–Oliver syndrome type 5 (AOS5), T-cell acute lymphoblastic leukemia (T-ALL), chronic lymphocytic leukemia, and squamous cell carcinoma of the head and neck. The gene discussed is NOTCH1; the disease is familial bicuspid aortic valve.