My dad just died of acute leukemia. He was in his late 70s. Is leukemia hereditary?

Usually not . Leukemia in adults is usually not hereditary. Sometimes individuals with other genetic changes such as down syndrome or a few other mutatations such as one called p53 have an increased risk, but most cases are not linked.
See below. Leukemia is generally not hereditary but having a first degree relative with leukemia may slightly increase your risk.