Cell division

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Not to be confused with cellular differentiation. Cell division_sentence_0

Cell division is the process by which a parent cell divides into two or more daughter cells. Cell division_sentence_1

Cell division usually occurs as part of a larger cell cycle. Cell division_sentence_2

In eukaryotes, there are two distinct types of cell division; a vegetative division, whereby each daughter cell is genetically identical to the parent cell (mitosis), and a reproductive cell division, whereby the number of chromosomes in the daughter cells is reduced by half to produce haploid gametes (meiosis). Cell division_sentence_3

In cell biology, mitosis (/maɪˈtoʊsɪs/) is a part of the cell cycle, in which, replicated chromosomes are separated into two new nuclei. Cell division_sentence_4

Cell division gives rise to genetically identical cells in which the total number of chromosomes is maintained. Cell division_sentence_5

In general, mitosis (division of the nucleus) is preceded by the S stage of interphase (during which the DNA is replicated) and is often followed by telophase and cytokinesis; which divides the cytoplasm, organelles and cell membrane of one cell into two new cells containing roughly equal shares of these cellular components. Cell division_sentence_6

The different stages of Mitosis all together define the mitotic (M) phase of an animal cell cycle—the division of the mother cell into two daughter cells genetically identical daughter cells. Cell division_sentence_7

Meiosis results in four haploid daughter cells by undergoing one round of DNA replication followed by two divisions. Cell division_sentence_8

Homologous chromosomes are separated in the first division, and sister chromatids are separated in the second division. Cell division_sentence_9

Both of these cell division cycles are used in the process of sexual reproduction at some point in their life cycle. Cell division_sentence_10

Both are believed to be present in the last eukaryotic common ancestor. Cell division_sentence_11

Prokaryotes (bacteria and archaea) usually undergo a vegetative cell division known as binary fission, where their genetic material is segregated equally into two daughter cells. Cell division_sentence_12

While binary fission may be the means of division by most prokaryotes, there are alternative manners of division, such as budding, that have been observed. Cell division_sentence_13

All cell divisions, regardless of organism, are preceded by a single round of DNA replication. Cell division_sentence_14

For simple unicellular microorganisms such as the amoeba, one cell division is equivalent to reproduction – an entire new organism is created. Cell division_sentence_15

On a larger scale, mitotic cell division can create progeny from multicellular organisms, such as plants that grow from cuttings. Cell division_sentence_16

Mitotic cell division enables sexually reproducing organisms to develop from the one-celled zygote, which itself was produced by meiotic cell division from gametes. Cell division_sentence_17

After growth, cell division by mitosis allows for continual construction and repair of the organism. Cell division_sentence_18

The human body experiences about 10 quadrillion cell divisions in a lifetime. Cell division_sentence_19

The primary concern of cell division is the maintenance of the original cell's genome. Cell division_sentence_20

Before division can occur, the genomic information that is stored in chromosomes must be replicated, and the duplicated genome must be separated cleanly between cells. Cell division_sentence_21

A great deal of cellular infrastructure is involved in keeping genomic information consistent between generations. Cell division_sentence_22

Cell division in Bacteria Cell division_section_0

Bacterial cell division happens through binary fission or budding. Cell division_sentence_23

The Divisome is a protein complex in bacteria that is responsible for cell division, constriction of inner and outer membranes during division, and peptidoglycan (PG) synthesis at the division site. Cell division_sentence_24

A tubulin like protein, FtsZ plays a critical role in formation of a contractile ring for the cell division. Cell division_sentence_25

Cell Division in Eukaryote Cell division_section_1

See also: Alternation of generations Cell division_sentence_26

Cell division in eukaryote is much more complicated than prokaryote. Cell division_sentence_27

Depending upon chromosomal number reduced or not; Eukaryotic cell divisions can be classified as Mitosis (equational division) and Meiosis (reductional division). Cell division_sentence_28

A primitive form of cell division is also found which is called amitosis. Cell division_sentence_29

The amitotic or mitotic cell division is more atypical and diverse in the various groups of organisms such as protists (namely diatoms, dinoflagellates etc) and fungi. Cell division_sentence_30

In mitotic metaphase (see below), typically the chromosomes (each with 2 sister chromatid that they developed due to replication in the S phase of interphase) arranged and sister chromatids split and distributed towards daughter cells. Cell division_sentence_31

In meiosis, typically in Meiosis-I the homologous chromosomes are paired and then separated and distributed into daughter cells. Cell division_sentence_32

Meiosis-II is like mitosis where the chromatids are separated. Cell division_sentence_33

In human and other higher animals and many other organisms, the meiosis is called gametic meiosis, that is the meiosis gives rise to gametes. Cell division_sentence_34

Whereas in many groups of organisms, especially in plants (observable in lower plants but vestigial stage in higher plants), the meiosis gives rise to the kind of spores that germinate into haploid vegetative phase (gametophyte). Cell division_sentence_35

This kind of meiosis is called sporic meiosis. Cell division_sentence_36

Phases of eukaryotic cell division Cell division_section_2

Variants Cell division_section_3

Cells are broadly classified into two main categories: simple non-nucleated prokaryotic cells and complex nucleated eukaryotic cells. Cell division_sentence_37

Due to their structural differences, eukaryotic and prokaryotic cells do not divide in the same way. Cell division_sentence_38

Also, the pattern of cell division that transforms eukaryotic stem cells into gametes (sperm cells in males or egg cells in females), termed meiosis, is different from that of the division of somatic cells in the body. Cell division_sentence_39

Image of the mitotic spindle in a human cell showing microtubules in green, chromosomes (DNA) in blue, and kinetochores in red. Cell division_sentence_40

Degradation Cell division_section_4

Multicellular organisms replace worn-out cells through cell division. Cell division_sentence_41

In some animals, however, cell division eventually halts. Cell division_sentence_42

In humans this occurs, on average, after 52 divisions, known as the Hayflick limit. Cell division_sentence_43

The cell is then referred to as senescent. Cell division_sentence_44

With each division the cells telomeres, protective sequences of DNA on the end of a chromosome that prevent degradation of the chromosomal DNA, shorten. Cell division_sentence_45

This shortening has been correlated to negative effects such as age related diseases and shortened lifespans in humans. Cell division_sentence_46

Cancer cells, on the other hand, are not thought to degrade in this way, if at all. Cell division_sentence_47

An enzyme complex called telomerase, present in large quantities in cancerous cells, rebuilds the telomeres through synthesis of telomeric DNA repeats, allowing division to continue indefinitely. Cell division_sentence_48

History Cell division_section_5

A cell division under microscope was first discovered by German botanist Hugo von Mohl in 1835 as he worked over the green alga Cladophora glomerata. Cell division_sentence_49

In 1943, cell division was filmed for the first time by Kurt Michel using a phase-contrast microscope. Cell division_sentence_50

See also Cell division_section_6

Cell division_unordered_list_0


Credits to the contents of this page go to the authors of the corresponding Wikipedia page: en.wikipedia.org/wiki/Cell division.