MEIOSIS

15.05.2021

Definition: 

A type of cell division in which a nucleus divides into four daughter nuclei, each containing half the chromosome number of the parent nucleus: occurs in all sexually reproducing organisms in which haploid gametes or spores are produced.   

It is cell's sexual reproduction. The number of chromosomes is reduced to half in order to form haploid cells, also called gamets. 

There are two consecutive divisions that reduce the genetic information. In order not to lose the information, as already explained in a previous article, there is dulication before the meiosis. 

Phases of meiosis 

Meiosis occurs through a two-stage cell division process: meiosis I and meiosis II

Meiosis I 

Meiosis I, also known as the reductive phase, is the stage where pairs of homologous cells separate, resulting in the genetic material of daughter cells being half that of progenitor cells. This is what generates genetic diversity. It is subdivided into four phases:

Prophase I: the chromosomes condense and form pairs. Cross-linking and genetic recombination occurs, allowing parts of DNA strands to be exchanged, giving rise to new genetic material.

Metaphase I: Homologous pairs line up on the metaphase plate for separation to occur.

Anaphase I: Chromosomes separate by moving to opposite ends of cells, while sister chromatids stay together.

Telophase I: Haploid cells are formed. Each chromosome will have two sister chromatids, which will no longer be the same as each other.

Meiosis II 

Meiosis II, also called the duplicative phase, is the stage in which the chromatids separate, producing a pair of daughter cells that each contain 23 chromosomes, and where each chromosome has, in turn, a single chromatid.

Prophase II: chromosomes condense.

Metaphase II - Chromosomes line up on the metaphase plate.

Anaphase II: sister chromatids separate at opposite ends of the cell.

Telophase II: newly formed gametes are haploid. Each chromosome has only one chromatid. The end product of meiosis is sperm or eggs.

Importance of meiosis 

Meiosis is a process of vital importance to carry out the life cycle, since it allows the survival of the species by producing sex cells or gametes, as well as genetic recombination.

In this sense, in meiosis genetic variability occurs between living beings of the same species that, although they share and inherit a series of characteristics, are unique beings because their genetic information is new.

It should be noted that genetic recombination of the father and mother chromosomes occurs randomly in the processes that correspond to Anaphase I and Anaphase II.

Meiosis and mitosis 

Meiosis and mitosis are different forms of cell division. In meiosis, sex cells or gametes are generated, that is, ovaries and sperm; It is the basis of sexual reproduction and essential for genetic variability to occur. The result of meiosis is cells with different genetic material.

Mitosis, on the other hand, is the process of cell division in which new cells are generated with identical genetic material. In this sense, mitosis is the cellular process responsible for asexual reproduction. It is essential for the growth and regeneration of tissues.

Check the other articles about cell biology!