OCR General Certificate of Secondary Education (GCSE) Biology Practice Exam

During which stage of meiosis do chromosomes line up in the center of the nucleus?

1. Stage 1

2. Stage 3

3. Stage 4

4. Stage 6

The correct answer is: Stage 3

During meiosis, the stage in which chromosomes line up in the center of the nucleus occurs during metaphase. Specifically, this is seen in Metaphase I of meiosis. This is the stage where homologous chromosome pairs align along the metaphase plate. The alignment is crucial for the proper separation of chromosomes, ensuring that each daughter cell receives the correct number of chromosomes. During this alignment, the spindle fibers, which are important for separating the chromosomes, attach to the kinetochores located on the centromeres of the chromosomes. This organization ensures that when the chromosomes are pulled apart in the next stage, the distribution to the daughter cells is even and accurate. Understanding this process is essential for grasping fundamental genetic mechanisms and the importance of meiosis in sexual reproduction.