Nuclear envelopes form around the chromosomes. The chromosomes arrive at opposite poles and begin to decondense. In anaphase II, the sister chromatids separate. In prometaphase II, microtubules attach to the kinetochores of sister chromatids, and the sister chromatids are arranged at the midpoint of the cells in metaphase II. In anaphase I, the homologous chromosomes separate. In prometaphase I, microtubules attach to the fused kinetochores of homologous chromosomes, and the homologous chromosomes are arranged at the midline of the cell (the metaphase plate) in metaphase I. The process of chromosome alignment differs between meiosis I and meiosis II. Nonkinetochore microtubules elongate the cell. The sister chromatids are pulled apart by the kinetochore microtubules and move toward opposite poles. The sister chromatids are maximally condensed and aligned at the equator of the cell. Each sister chromatid forms an individual kinetochore that attaches to microtubules from opposite poles. The nuclear envelopes are completely broken down, and the spindle is fully formed. The MTOCs that were duplicated during interkinesis move away from each other toward opposite poles, and new spindles are formed. If nuclear envelopes were formed, they fragment into vesicles. If the chromosomes decondensed in telophase I, they condense again. In terms of chromosomal content, cells at the start of meiosis II are similar to haploid cells in G 2, preparing to undergo mitosis. Therefore, each cell has half the number of sister chromatids to separate out as a diploid cell undergoing mitosis. The mechanics of meiosis II are similar to mitosis, except that each dividing cell has only one set of homologous chromosomes, each with two chromatids. During meiosis II, the sister chromatids within the two daughter cells separate, forming four new haploid gametes. The two cells produced in meiosis I go through the events of meiosis II in synchrony. Interkinesis lacks an S phase, so chromosomes are not duplicated. In some species, cells enter a brief interphase, or interkinesis, before entering meiosis II.
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