There are two types of cell divisions in eukaryotes: mitosis, regarding somatic cells and which provides an identical cell to the parent cell during the asexual multiplication cells (it thus preserves genetic information) and meiosis resulting in production of sexual cells or gametes for reproduction.

For animals, meiosis is a process that takes place during gametogenesis (spermatogenesis or ovogenesis), that is to say during the development of gametes (sperm in males and eggs in females) in the so-called species diploid.

In plants, meiosis produces spores which give by mitosis haploid generation (pollen, leafy foot foam, etc. . ) It gives haploid cells (cells containing n chromosomes) from diploid cells (cell containing 2n chromosomes - in humans, a normal cell contains 2n = 46 chromosomes (ie 23 pairs), while a gamete contains n = 23 chromosomes in two divisions). In haploid species (such as Sordaria macrospora ), meiosis occurs after fertilization to divide the egg cell ( 2n chromosomes). But in addition to the role of division, meiosis has an important role in genetic mixing (miscegenation), thanks to two mechanisms shuffling: the interchromosomal and intrachromosomal shuffling) .

Thus, during meiosis, the amount of DNA within the cell varies over time.

Each cell will therefore separate genetic heritage (contained in chromosomes) in two to transmit only half of their genes to daughter cells.

It takes place in several stages forming a set of two cell divisions, successive and inseparable.

The first meiotic division is reductional, because it changes a 2n double chromosome cell into a n double chromosome cell.

The second is called equational because it keeps the number of chromosomes: one passes from n to n simple double chromosomes.

Meiosis allows the formation of four haploid daughter cells (or gametes).

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