Meaning Meiosis

Overview of the major events in meiosis

Meiosis (a Greek word meaning "decrease") is a cellular process that forms the basis for sexual reproduction, together with syngamy. It is a form of nuclear division by which a diploid parent produces four haploid daughter cells. The process includes the two stages of nuclear division (meiosis I and II), usually accompanied by cell division. Single-stage meiosis has been suggested but not convincingly demonstrated. Duplication of chromosomes precedes the process of meiosis. Most animals and plants are normally diploid, and use meiosis to produce gametes, which fuse to form zygotes that develop into new organisms. This is often the primary or only means of proliferation. In other eukaryotes, sexual reproduction may play a more restricted role.

The mechanistic differences between mitosis, which produces somatic cells, and meiosis, is best understood by considering mitosis first. (All jargon used in this article is defined in the article on mitosis.)

As described earlier, meiotic nuclear division consists of two stages, called meiosis I and meiosis II. It starts with a cell in the same state as does a mitotic division. However, the alignment of chromosomes for prophase is different. Homologous chromosomes join into tetrads (so called because each tetrad contains four chromatids), and the tetrads line up on the metaphase plane.

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