Mitosis and meiosis are two different forms of cell division in eukaryotic cells, those that possess a nucleus.
During the cell cycle, the eukaryotic cell undergoes a series of changes that lead to the formation of new cells. Depending on the type of cell, it can divide by mitosis or meiosis.
For example, in organisms that have sexual reproduction, germ cells divide by meiosis to give rise to sex cells or gametes. On the other hand, somatic cells only divide through mitosis.
|Definition||Nuclear division process in which two nuclei with the same number of chromosomes in the source cell are generated.||Nuclear division process that gives rise to four cells with half the number of chromosomes in the original cell.|
|Stages or phases||
|Number of nuclear divisions||1||2|
|Number of genetic duplications||1||1|
|Chromosomal crossover and recombination||Absent.||Present in prophase I and metaphase I.|
|Result||Two daughter cells with the same amount of genetic material.||Four cells with half the genetic material.|
|Example||Dermis cells proliferate to renew skin cells.||Germ cells located in the gonads produce gametes.|
The mitosis is a process of cell division that occurs in the nucleus of eukaryotic cells, subsequent to the duplication of the genetic material at the interface. This process is present in both unicellular and multicellular beings. It is also known as karyokinesis.
In mitosis, a diploid cell gives rise to two diploid cells with the same genetic information.
Phases of mitosis
Mitosis is a continuous process where the following successive phases can be identified:
- Profase: the genetic material begins to condense and form long, thin threads. The mitotic spindle is formed.
- Prometaphase: disappearance of the nuclear envelope or karyoteca.
- Metaphase: location of chromosomes at the cellular equator.
- Anaphase: chromosomes migrate to the poles of the cell.
- Telophase: at each pole of the cell begins to reorganize the nuclear envelope surrounding the chromosomes that are already decompressing.
Mitosis is followed by the process of cytokinesis o cytodereesisthat is, the division of the cytoplasm to give rise to two daughter cells.
In this video you can see the formation of the mitotic spindle, which is this structure as a starfish with yellow center and red tentacles. Chromosomes look like chubby worms, which are being dragged by spindles to opposite ends of the cell.
Animation of the mitosis process where the stages of prophase, metaphase, anaphase and telophase are shown.
Importance of mitosis
Mitosis occurs in undifferentiated somatic cells and pluripotent cells. Its importance lies in the fact that it is essential for the following cellular processes:
- Development: from the zygote, which is the first cell of a multicellular individual, the millions of different cells that make up a higher organism are generated.
- Growth: allows an increase in the number of cells in organisms, promoting their growth.
- Tissue repair and renewal: through mitosis new cells are regenerated to replace cells that die or are lost.
You may also be interested in seeing Phases of Mitosis.
Meiosis is the process of cell division of a diploid cell (2nd) to give rise to four haploid cells (1st). The result is the gametes or sex cells: sperm in the male and eggs in females of most species.
The general process of meiosis involves two successive nuclear divisions, without duplication of genetic material in the intermediate step. In addition, chromosomal cross-linking and recombination occurs, so the resulting four cells do not necessarily carry the same genetic information.
Phases of meiosis
Because meiosis occurs after two nuclear divisions, known as meiosis I and meiosis II, the phases are given the same name as the stages of mitosis followed by the number of the period in which they occur:
- Profase I: homologous chromosomes mate and exchange genetic material for crossbreeding.
- Metaphase I: Chromosomes are located at the equator of the cell at random.
- Anaphase I: Homologous chromosomes separate and go to the poles of the cell.
- Telophase I: Chromosomes already in the poles begin to disorganize and be surrounded by the nuclear envelope.
At the end of this first period of cell division, two diploid cells with the same amount of genetic material are obtained.
Period I daughter cells enter a short II interface, where chromosomes disorganize and there is no genetic duplication.
- Profase II: Chromatin is condensed again and the nuclear envelope disappears.
- Metaphase II: Chromosomes formed by two chromatids are located at the equator of the cell.
- Anaphase II: sister chromatids separate and are carried to the poles of the cell.
- Telophase II: Chromosomes now with a single chromatid are at the poles and the nuclear envelope around them begins to reorganize.
At the end of this second period of nuclear division, the result is four haploid cells, each with half the genetic material.
Importance of meiosis
Meiosis occurs only in cells that will give rise to gametes, or germ cells. Thanks to this process, a cell with a chromosomal load equal to 2nd generates four cells with chromosomal load 1st.
In meiosis genetic recombination of homologous chromosomes occurs, which increases genetic variability in species.
Gametogenesis is the process of formation of gametes or sex cells, which possess half of the 1st chromosomal load (haploids). When two gametes, one male and one female, fuse, a 2nd diploid cell is formed, that is, with the full genetic load of the species.
Comparison of the process of mitosis and meiosis
We could compare the processes of mitosis and meiosis as follows: The mitosis of a cell is like the photocopy of a page of a book, with the end result of two pages with the same content. While cell meiosis is a page from a book that we photocopied and then split in two, resulting in four pieces of paper with partially different content.
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