Which is the first phase of mitosis?

• A. Metaphase
• B. Prophase
• C. Anaphase
• D. Telophase

Answer: (B)

Understanding the order of mitotic events. The first phase of mitosis is prophase. In this stage, chromatin condenses into visible chromosomes, the nucleolus disappears, and the mitotic spindle begins to form as centrosomes move to opposite poles. The nuclear envelope starts to break down so spindle fibers can interact with the chromosomes, setting up the machinery needed for orderly separation. After prophase come later stages where chromosomes align at the center, sister chromatids are pulled apart, and new nuclei form around the separated sets. Metaphase features chromosomes lining up at the cell’s center; anaphase pulls chromatids toward opposite poles; and telophase re-forms the nuclei and begins chromosome de-condensation. Prophase is the first phase because it starts chromosome condensation and spindle formation that drive the rest of the process.