Meiosis

Meiosis Meiosis is a process of nuclear division that reduces the number of chromosomes in new cells to half the number in the original cell. Meiosis leads to four haploid cells (gametes) rather than two diploid cells as in mitosis.

Meiosis I Meiosis I includes prophase I, metaphase I, anaphase I, and telophase I. Crossing-over, which is when portions of homologous chromosomes exchange genetic material, occurs during prophase I and results in genetic recombination.

Meiosis I Prophase I – chromosomes become visible, pairs meet, crossing over occurs so sister chromatids are no longer identical Metaphase I – pairs of chromosomes line up

Meiosis I Anaphase I – chromosome pairs are separated Telophase – haploid cells with duplicated chromosomes are produced

Meiosis II Meiosis II includes prophase II, metaphase II, anaphase II, and telophase II. Four new haploid cells result.

Meiosis II Prophase II – chromosomes remain visible Metaphase II – chromosomes line up in the center of the cell

Meiosis II Anaphase II – sister chromatids are pulled apart Telophase II – four haploid cells that are not identical are created.

Comparing Mitosis and Meiosis

Development of Gametes Spermatogenesis is the process by which sperm cells are produced. Oogenesis is the process that produces mature egg cells.