Meiosis
(Redirected from Meioses)
Meiosis is a type of cell division that reduces the number of chromosomes in the parent cell by half and produces four gamete cells. This process is required to produce egg and sperm cells for sexual reproduction.
Overview[edit | edit source]
During meiosis, one cell undergoes two successive divisions, with the result of four cells, each with half the number of chromosomes of the original cell. The stages of meiosis, including prophase, metaphase, anaphase and telophase, happen twice. The first division is referred to as meiosis I and the second as meiosis II.
Meiosis I[edit | edit source]
Meiosis I is characterized by the pairs of homologous chromosomes coming together and crossing over. The paired and replicated chromosomes are separated into two cells during meiosis I. This step is unique to meiosis.
Prophase I[edit | edit source]
During prophase I, the chromosomes condense and pair up. The nuclear envelope breaks down, and spindle fibers form.
Metaphase I[edit | edit source]
In metaphase I, the paired chromosomes align at the cell's equator. These pairs are then pulled apart by the spindle fibers.
Anaphase I[edit | edit source]
During anaphase I, the spindle fibers pull the paired chromosomes toward opposite ends of the cell.
Telophase I and Cytokinesis[edit | edit source]
In telophase I, the chromosomes gather at the poles of the cells. Then, the cytoplasm divides.
Meiosis II[edit | edit source]
Meiosis II is similar to mitosis. However, the result is four daughter cells, rather than two.
Prophase II[edit | edit source]
During prophase II, the nuclear envelope breaks down and the spindle fibers form.
Metaphase II[edit | edit source]
In metaphase II, the chromosomes align at the equator, just like in a mitotic cell.
Anaphase II[edit | edit source]
During anaphase II, the sister chromatids are pulled apart by the spindle fibers and move toward opposite ends of the cell.
Telophase II and Cytokinesis[edit | edit source]
In telophase II, the chromosomes gather at the poles of the cells and the nuclear envelope re-forms. Then, the cytoplasm divides.
Significance[edit | edit source]
Meiosis is necessary for sexual reproduction in eukaryotes, such as animals, plants and fungi. It ensures that offspring have the same number of chromosomes as the parent. The process also increases genetic variation by shuffling the genes between the two parent cells.
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