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.