Cell division is the process by which a parent cell divides into two
or more daughter cells.
Cell division usually occurs as part of a
larger cell cycle. 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 results in four haploid daughter cells by
undergoing one round of
DNA replication followed by two divisions.
Homologous chromosomes are separated in the first division, and sister
chromatids are separated in the second division. Both of these cell
division cycles are used in the process of sexual reproduction at some
point in their life cycle. Both are believed to be present in the last
eukaryotic common ancestor. Prokaryotes undergo a vegetative cell
division known as binary fission, where their genetic material is
segregated equally into two daughter cells. All cell divisions,
regardless of organism, are preceded by a single round of DNA
For simple unicellular microorganisms such as the amoeba, one cell
division is equivalent to reproduction – an entire new organism is
created. On a larger scale, mitotic cell division can create progeny
from multicellular organisms, such as plants that grow from cuttings.
Mitotic cell division enables sexually reproducing organisms to
develop from the one-celled zygote, which itself was produced by
meiotic cell division from gametes. After growth, cell division by
mitosis allows for continual construction and repair of the
organism. The human body experiences about 10 quadrillion cell
divisions in a lifetime.
The primary concern of cell division is the maintenance of the
original cell's genome. 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. A great
deal of cellular infrastructure is involved in keeping genomic
information consistent between generations.
1 Phases of cell division
5 See also
7 Further reading
8 External links
Phases of cell division
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Interphase is the process a cell must go through before mitosis,
meiosis, and cytokinesis.
Interphase consists of four main stages:
G1, S, G0, and G2. G1 is a time of growth for the cell. If the cell
does not progress through G1, the cell then enters a stage called G0.
In G0, cells are still living but they are put on hold. The cells may
later be called back into interphase if needed at a later time. There
are checkpoints during interphase that allow the cell to be either
progressed or denied further development. In S phase, the chromosomes
are replicated in order for the genetic content to be maintained.
During G2, the cell undergoes the final stages of growth before it
enters the M phase. The M phase, can be either mitosis or meiosis
depending on the type of cell. Germ cells undergo meiosis, while
somatic cells will undergo mitosis. After the cell proceeds
successfully through the M phase, it may then undergo cell division
through cytokinesis. The control of each checkpoint is controlled by
cyclin and cyclin dependent kinases. The progression of interphase is
the result of the increased amount of cyclin. As the amount of cyclin
increases, more and more cyclin dependent kinases attach to cyclin
signaling the cell further into interphase. The peak of the cyclin
attached to the cyclin dependent kinases this system pushes the cell
out of interphase and into the M phase, where mitosis, meiosis, and
Prophase is the first stage of division. The nuclear envelope is
broken down, long strands of chromatin condense to form shorter more
visible strands called chromosomes, the nucleolus disappears, and
microtubules attach to the chromosomes at the kinetochores present in
the centromere. Microtubules associated with the alignment and
separation of chromosomes are referred to as the spindle and spindle
Chromosomes will also be visible under a microscope and will
be connected at the centromere. During this condensation and alignment
period, homologous chromosomes may swap portions of their DNA in a
process known as crossing over.
Metaphase is the stage in cell division when the chromosomes line up
in the middle of the cell by MTOCs ( microtubule organizing center) by
pushing and pulling on centromeres of both chromatids which causes the
chromosome to move to the center. The chromosomes are still condensing
and are currently at one step away from being the most coiled and
condensed they will be. Spindle and spindle fibers have already
connected to the kinetochores. At this point, the chromosomes are
ready to split into opposite poles of the cell towards the spindle to
which they are connected. 
Anaphase is a very short stage of the cell cycle and occurs after the
chromosomes align at the mitotic plate. After the chromosomes line up
in the middle of the cell, the spindle fibers will pull them apart.
The chromosomes are split apart as the sister chromatids move to
opposite sides of the cell.
Telophase is the last stage of the cell cycle. Two cells form around
the chromatin at the two poles of the cell. Two nuclear membranes
begin to reform and the chromatin begin to unwind.
Image of the mitotic spindle in a human cell showing microtubules in
green, chromosomes (DNA) in blue, and kinetochores in red.
Cells are broadly classified into two main categories: simple,
non-nucleated prokaryotic cells, and complex, nucleated eukaryotic
cells. Owing to their structural differences, eukaryotic and
prokaryotic cells do not divide in the same way. 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 over 42. The cells were directly imaged in the cell
culture vessel, using non-invasive quantitative phase contrast
Multicellular organisms replace worn-out cells through cell division.
In some animals, however, cell division eventually halts. In humans
this occurs, on average, after 52 divisions, known as the Hayflick
limit. The cell is then referred to as senescent. Cells stop dividing
because the telomeres, protective bits of DNA on the end of a
chromosome required for replication, shorten with each copy,
eventually being consumed.
Cancer cells, on the other
hand, are not thought to degrade in this way, if at all. An enzyme
called telomerase, present in large quantities in cancerous cells,
rebuilds the telomeres, allowing division to continue indefinitely.
Kurt Michelwith his phase-contrast microscope
A cell division under microscope was first discovered by German
Hugo von Mohl
Hugo von Mohl in 1835 as he worked over Green algae
In 1943, cell division was filmed for the first time, by Kurt
Michelwith, using a phase-contrast microscope.
Labile cells, cells that constantly divide
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J.M.Turner Fetus into Man (1978, 1989). Harvard University Press.
Cell division: binary fission and mitosis
Wikimedia Commons has media related to Cell division.
How Cells Divide:
Mitosis vs. Meiosis
Mitosis and Cell Cycle Control Section from the Landmark Papers in
Cell Biology (Gall JG, McIntosh JR, eds.) contains commentaries on and
links to seminal research papers on mitosis and cell division.
Published online in the Image & Video Library of The American
Society for Cell Biology
The Image & Video Library of The American Society for Cell Biology
contains many videos showing the cell division.
The Cell Division of the Cell Image Library
Videos of the first cell divisions in
Xenopus laevis embryos (side
view and top view), acquired by
MRI (DOI of paper)
Images : Calanthe discolor Lindl. - Flavon's Secret Flower Garden
Tyson's model of cell division and a Description on BioModels Database
WormWeb.org: Interactive Visualization of the C. elegans Cell Lineage
- Visualize the entire set of cell divisions of the nematode C.
Cell cycle proteins
A (A1, A2)
B (B1, B2, B3)
D (D1, D2, D3)
E (E1, E2)
INK4a/ARF (p14arf/p16, p15, p18, p19)
cip/kip (p21, p27, p57)
P53 p63 p73 family
Cellular apoptosis susceptibility protein
Maturation promoting factor
Cell cycle checkpoints
Other cellular phases