Meiosis II

Meiosis II is the second division of meiosis. It may begin immediately after meiosis I or after a short resting stage called interkinesis. During this interval, no DNA replication takes place.

Like mitosis, meiosis II is an equational division. In this division, each haploid cell divides into two new haploid cells.

Meiosis II includes prophase II, prometaphase II, metaphase II, anaphase II, and telophase II.

Prophase II begins when replicated chromosomes condense again. Each chromosome contains two sister chromatids joined at a centromere. Because crossing over happens during meiosis I, sister chromatids may carry new combinations of maternal and paternal genetic material.

At the same time, centrosomes move toward opposite poles of the cell. The spindle apparatus forms between them.

During prometaphase II, the nuclear envelope breaks down. This allows chromosomes to move freely within the cell. Protein complexes called kinetochores on the centromeres attach to spindle microtubules extending from opposite poles.

In metaphase II, spindle microtubules align the chromosomes along the cell’s equator.

During anaphase II, cohesin proteins at the centromere, which hold the sister chromatids together, break down. The spindle microtubules shorten and pull sister chromatids apart toward opposite poles. At the same time, the cell elongates.

During telophase II, the chromatids reach opposite poles of the cell. Each group forms a haploid set of unreplicated chromosomes.

Next, the chromosomes unwind, new nuclear envelopes form, and the cell undergoes cytokinesis.

Meiosis II produces four haploid cells with unique genetic combinations. In animals, these cells can develop into gametes.