Question

during which phase of mitosis do sister chromatids line up at the center of the cell?
prophase
metaphase
telophase
anaphase

Explanation:

To solve this, we recall the phases of mitosis:

• Prophase: Chromosomes condense, spindle forms, nuclear envelope breaks down. Sister chromatids don't line up at the center here.
• Metaphase: Sister chromatids (attached to spindle fibers) align at the cell's equatorial plate (center).
• Telophase: Chromosomes decondense, nuclear envelopes reform. Alignment at center is not a feature here.
• Anaphase: Sister chromatids separate and move to opposite poles. They don't line up at the center here.

So the phase where sister chromatids line up at the center is Metaphase.

Answer:

B. Metaphase