During which phase of mitosis does the mitotic spindle begin to form?

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

Answer: (C)

Verified step by step guidance

1. Understand the process of mitosis, which is divided into distinct phases: prophase, metaphase, anaphase, and telophase. Each phase has specific events that occur to ensure proper cell division.
2. Recall that the mitotic spindle is a structure made of microtubules and associated proteins. It plays a critical role in separating chromosomes during mitosis.
3. Focus on the events of prophase. During this phase, the chromatin condenses into visible chromosomes, and the nuclear envelope begins to break down. Importantly, the mitotic spindle starts to form as microtubules extend from the centrosomes.
4. Compare prophase to the other phases listed in the problem: metaphase, anaphase, and telophase. In metaphase, chromosomes align at the cell's equatorial plane; in anaphase, sister chromatids are pulled apart; and in telophase, the nuclear envelope reforms around separated chromosomes. None of these phases involve the initial formation of the mitotic spindle.
5. Conclude that the correct phase during which the mitotic spindle begins to form is prophase, as this is the phase where the spindle assembly starts and prepares for chromosome alignment in later stages.