Familial Hypercholesterolemia LDLR Heterozygous

A 42-year-old man presents to the cardiac catheterization lab with acute anterior STEMI. Examination reveals bilateral tendon xanthomas on the Achilles tendons, tuberous xanthomas on the elbows, xanthelasma, and corneal arcus. Lipid panel shows total cholesterol 412 mg/dL and LDL-C 332 mg/dL. His father died of MI at age 38, and his 14-year-old son has LDL-C of 280 mg/dL. Genetic testing confirms a heterozygous pathogenic mutation in the LDLR gene. The inheritance pattern shown in the pedigree, marked as **A** in the diagram, is characterized by which of the following features?