Meiosis I results in two cells, called daughter cells. However, because each pair of homologous chromosomes was separated, neither daughter cell has the two complete sets of chromosomes that it would have in a diploid cell. Those two sets have been shuffled and sorted almost like a deck of cards. The two cells produced by meiosis I have sets of chromosomes and alleles that are different from each other and from the diploid cell that entered meiosis I.

Meiosis II The two cells now enter a second meiotic division. Unlike the first division, neither cell goes through a round of chromosome replication before entering meiosis II.

▸ Prophase II As the cells enter prophase II, their chromosomes—each consisting of two chromatids—become visible. The chromosomes do not pair to form tetrads, because the homologous pairs were already separated during meiosis I.

▸ Metaphase II, Anaphase II, Telophase II, and Cytokinesis During metaphase of meiosis II, chromosomes line up in the center of each cell. As the cell enters anaphase, the paired chromatids separate. The final four phases of meiosis II are similar to those in meiosis I. However, the result is four haploid daughter cells. In the example shown here, each of the four daughter cells produced in meiosis II receive two chromosomes. These four daughter cells now contain the haploid number (N)—just two chromosomes each.

Gametes to Zygotes The haploid cells produced by meiosis II are the gametes that are so important to heredity. In male animals, these gametes are called sperm. In some plants, pollen grains contain haploid sperm cells. In female animals, generally only one of the cells produced by meiosis is involved in reproduction. The female gamete is called an egg in animals and an egg cell in some plants. After it is fertilized, the egg is called a zygote (ZY goht). The zygote undergoes cell division by mitosis and eventually forms a new organism.

In Your Notebook Describe the difference between meiosis I and meiosis II. How are the end results different?

FIGURE 11–16 Meiosis II The second meiotic division, called meiosis II, produces four haploid daughter cells.

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