How is metaphase I different from metaphase II in meiosis?

• A. In metaphase I, homologous chromosomes line up at the equatorial plate, while in metaphase II, sister chromatids line up.
• B. In metaphase I, chromosomes are not aligned at the equatorial plate, while in metaphase II, they are.
• C. In metaphase I, the nuclear envelope reforms, while in metaphase II, it breaks down.
• D. In metaphase I, sister chromatids line up at the equatorial plate, while in metaphase II, homologous chromosomes line up.

Answer: (A)

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, resulting in the production of gametes or spores. It consists of two consecutive divisions: meiosis I and meiosis II.
2. Identify the key events in metaphase I: During metaphase I, homologous chromosomes (each consisting of two sister chromatids) line up along the equatorial plate of the cell. This alignment is crucial for the separation of homologous chromosomes in the subsequent anaphase I.
3. Identify the key events in metaphase II: In metaphase II, the sister chromatids of each chromosome line up along the equatorial plate. This is similar to metaphase in mitosis, but it occurs in haploid cells resulting from meiosis I.
4. Compare the alignment of chromosomes: In metaphase I, the focus is on the alignment of homologous chromosomes, whereas in metaphase II, the focus is on the alignment of sister chromatids.
5. Clarify the role of the nuclear envelope: The nuclear envelope does not reform during metaphase I; instead, it breaks down during prophase I and remains disassembled through metaphase I. In metaphase II, the nuclear envelope is already broken down from the previous stages of meiosis II.