Step 1: Understand the phases of the cell cycle, which includes interphase and mitosis. Interphase is the phase where the cell prepares for division, but it is not part of mitosis itself.
Step 2: Recall that mitosis consists of specific phases: prophase, metaphase, anaphase, and telophase. These phases describe the process of chromosome alignment, separation, and division of the nucleus.
Step 3: Identify each phase listed in the problem: Anaphase, Metaphase, and Prophase are all recognized phases of mitosis.
Step 4: Recognize that Interphase is not a phase of mitosis but rather the phase before mitosis where the cell grows and DNA is replicated.
Step 5: Conclude that the correct answer to the question 'Which is NOT a phase of mitosis?' is Interphase, because it is part of the cell cycle but not part of mitosis itself.