A Level Biology Practice Exam

During which stage of mitosis do chromatids separate and move to opposite poles?

1. Prophase

2. Metaphase

3. Anaphase

4. Telophase

The correct answer is: Anaphase

The stage of mitosis in which chromatids separate and move to opposite poles is indeed Anaphase. During Anaphase, the cohesion that holds the sister chromatids together is cleaved, allowing them to become individual chromatids. These chromatids, now considered separate chromosomes, are then pulled toward opposite poles of the cell by the spindle fibers attached to their centromeres. This movement is crucial for ensuring that each daughter cell will receive an identical set of chromosomes when the cell divides. In contrast, in Prophase, the chromatin condenses into visible chromosomes, the nuclear envelope starts breaking down, and the mitotic spindle begins to form. Metaphase involves the alignment of chromosomes along the equatorial plane of the cell, where they are positioned in preparation for separation. Finally, during Telophase, the chromosomes reach the poles and begin to de-condense back into chromatin, while the nuclear envelope re-forms around each set of chromosomes, indicating that the cell is close to finishing mitosis. These stages all lead up to Anaphase, where the actual separation of the chromatids occurs.