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Difference Between Mitosis and Meiosis

difference between mitosis and meiosis

Difference Between Mitosis and Meiosis

Cell division is a process that occurs in all living organisms; it operates to bring about growth and development and make reproduction possible. The two main types of cell division are mitosis and meiosis. These two types are alike in that they both cause cell replication, but they are different in terms of their functions, outcomes, and genetic variation. These differences between mitosis and meiosis must be understood in genetics, biology, and medical research.

What are mitosis and meiosis?

Mitosis

Mitosis is the cell division during which a single cell divides into two identical daughter cells. This process occurs under typical conditions in the somatic cells of organisms, mainly concerning all growth, repair, and maintenance of an organism. Daughter cells will carry the same number of chromosomes as parental cells, comprising single-stage mitosis cell division. It works chiefly in tissue repair for asexual reproduction processes during cellular growth or replacing damaged cells.

Meiosis

Meiosis, on the other hand, occurs in reproductive cells; the final result of meiosis is four daughter cells, which exhibit genetic dissimilarity with one another. Meiosis, like mitosis, is a two-stage cell division in which two consecutive cell divisions bring about a halving of chromosome number. This basic reproductive process is sexual and affords genetic variation in the progeny. Meiosis is significant in producing genetically varied sperm and ovum for evolution and the continuation of species.

difference between mitosis and meiosis
Mitosis and Meiosis

 

What are the differences between mitosis and meiosis?

 

Basis of differentiation Mitosis Meiosis
Definition A type of cell division that results in two identical daughter cells having the same number of chromosomes as the parent cell A type of cell division that results in four daughter cells, each with half the number of chromosomes as its parent cell (for the production of gametes)
Cell division During mitosis, a somatic cell divides once, and cytokinesis occurs at the end of telophase. A reproductive cell divides twice; cytokinesis occurs at the end of telophase I and II. 
Daughter cell number Mitosis produces 2 daughter cells; each cell is diploid, containing the same number of chromosomes.  Meiosis produces 4 daughter cells; each cell is haploid, containing half the number of chromosomes as the parent cell. 
Length of prophase During prophase in mitosis, a cell spends less time in prophase than a cell in meiosis.  Prophase I has five stages and lasts longer than the prophase of mitosis. The five stages of meiotic prophase I are leptotene, zygotene, pachytene, diplotene, and diakinesis. 
Genetic composition/variation The resulting daughter cells in mitosis are genetically identical (no recombination or crossing over occurs and thus no genetic variation occurs) The resulting daughter cells have different combinations of genes. Genetic recombination occurs due to the random segregation of homologous chromosomes into different cells and through crossing over (genetic variation increases). 
Chromosome alignment in metaphase Sister chromatids align at the metaphase plate in mitosis  Tetrads align at the metaphase plate in metaphase I
Tetrad formation Tetrad formation does not occur. In prophase I, homologous chromosome pairs line up together forming tetrads (two sets of sister chromatids)
Chromosome separation  During anaphase, sister chromatids separate and migrate toward opposite poles of the cell. Homologous chromosomes migrate toward the opposite poles of the cell during anaphase I (sister chromatids don’t separate in anaphase I)
Steps  Has 6 steps in total  Has 9 steps in total 
Occurrence Occurs in somatic cells Occurs in germ cells 
Chromosome number  The chromosome number remains the same The chromosome number is halved in each daughter cell 
Purpose The purpose of mitosis is cell proliferation The purpose of meiosis is sexual reproduction 

The stages of mitosis vs. meiosis

The phases consist of interphase, prophase, metaphase, anaphase, and telophase, with the general outcome being cytokinesis. Interphase includes the pre-mitotic phase and the G1, S, and G2 phases. The stages of meiosis thus are interphase, prophase I, metaphase I, anaphase I, telophase I, cytokinesis I, prophase II, metaphase II, anaphase II, telophase II, and finally cytokinesis II. This will be explained further

 

Summary
Meiosis and mitosis both have prophase, metaphase, anaphase, telophase, and cytokinesis.
In meiosis, prophase, metaphase, anaphase, and telophase occur twice. The first round of division is special, but the second round is more like mitosis. In mitosis, prophase, metaphase, anaphase, and telophase occur once.
Prophase
Chromosomes condense and the centrosomes begin to form an early spindle.
  • Meiotic prophase I is much longer than mitotic prophase.
  • During prophase I, homologous chromosomes make contact with each other, called chiasmata, and “crossing over” occurs. This is where chromosomes exchange sections of DNA. This is important for generating genetic diversity but is also crucial mechanically to hold homologous chromosomes together.
  • Mitotic prophase is much shorter than meiotic prophase I.
  • There is no crossing over in mitosis.
Metaphase
In metaphase II of meiosis and metaphase of mitosis, chromosomes line up along the metaphase plate due to the action of microtubule spindle fibers emanating from the centrosomes located at opposite cell poles. These fibers are attached to the chromosomes by kinetochores at the centromeres of the chromosomes.
  • In meiotic metaphase I, pairs of homologous chromosomes line up along the metaphase plate.
  • How the homologous pairs are oriented randomly concerning the cell poles is referred to as the law of independent assortment and ensures a random and independent distribution of chromosomes to the daughter cells of meiosis I and ultimately to the haploid gametes at the end of meiosis II.
  • In mitotic metaphase, a single chromosome/pair of chromatids lines up along the metaphase plate.
  • Sister chromatids are identical, so the orientation of the chromosome doesn’t carry any meaning.
Anaphase
In anaphase, chromosomes are split to opposite poles of the cell.
  • In anaphase of meiosis I, cohesin at the centromeres of the chromosomes is not cleaved and it therefore continues to hold sister chromatids together as the homologous chromosomes are segregated to opposite cell poles.
  • In anaphase of mitosis (and meiosis II), cohesin protein holding the centromeres of the sister chromatids together is cleaved, allowing the sister chromatids to segregate to opposite poles of the cell, at which point they are called chromosomes.
Telophase
A nuclear membrane reforms around the newly separated chromosomes, which begin to uncoil, becoming less condensed. The spindle microtubules disassociate. Each daughter cell will inherit one centrosome.
Cytokinesis
The cell plasma membrane pinches to leave two daughter cells with separate plasma membranes.
  • In meiosis, cytokinesis must occur twice: once after telophase I and again after telophase II.
  • In mitosis, cytokinesis does not always occur; some cells divide and are multinucleated, like muscle cells.

Significance of Mitosis and Meiosis

Since before that time, mitosis has contributed to an organism’s growth and development in the sense that it multiplies its cells and forms tissues. It replaces damaged or dead cells and also serves as a means for the organism to heal during tissue repair, such as after injury. Mitosis enables certain microorganisms to produce offspring asexually, thus ensuring their continued existence on Earth without fertilization.

On the contrary, meiosis provides individual organisms required for sexual reproduction, thus leading to differences in progeny. The number of chromosomes in the gametes is halved in meiosis, ensuring that every new generation has the correct chromosome numbers. The genetic variation that results from this is necessary for evolution and adaptation so that living beings may survive when the environment changes.

Conclusion 

There is a marked difference between mitosis and meiosis, as they are processes involved in two entirely different functions. Through meiosis, genetic variation is achieved and perpetuated in all living beings. Mitosis is mainly concerned with cells’ growth and development. Mitosis would ensure the healing of genetic injuries occurring in germline cells.

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