Which of the following correctly describes a key difference between metaphase I and metaphase II during meiosis?

• A. Metaphase I occurs during mitosis, while metaphase II occurs during meiosis.
• B. In metaphase I, homologous chromosome pairs align at the metaphase plate, while in metaphase II, individual chromosomes align at the metaphase plate.
• C. In metaphase I, sister chromatids are separated, while in metaphase II, homologous chromosomes are separated.
• D. In metaphase II, crossing over occurs, but not in metaphase I.

Answer: (B)

Verified step by step guidance

1. Understand the context of meiosis: Meiosis is a type of cell division that reduces the chromosome number by half, producing four haploid cells. It consists of two stages: meiosis I and meiosis II.
2. Review metaphase I: During metaphase I, homologous chromosome pairs (each consisting of two sister chromatids) align at the metaphase plate. This alignment is crucial for the separation of homologous chromosomes during anaphase I.
3. Review metaphase II: During metaphase II, individual chromosomes (each still consisting of two sister chromatids) align at the metaphase plate. This stage is similar to metaphase in mitosis.
4. Compare the key difference: The main distinction is that in metaphase I, homologous chromosome pairs align at the metaphase plate, while in metaphase II, individual chromosomes align at the metaphase plate. This reflects the different purposes of the two stages in meiosis.
5. Clarify misconceptions: Metaphase I and metaphase II both occur during meiosis, not mitosis. Crossing over occurs during prophase I, not metaphase II. Additionally, sister chromatids are separated in anaphase II, not metaphase I.