Cell division is the process by which the stem cell is divided into two or more child cells. Cell division usually occurs as part of a larger cell cycle. In eukaryotes, there are two types of cell division: the vegetative division, in which every child cell is genetically identical to the stem cell (mitosis), and reproductive cell division, where the number of chromosomes in a child's cell is reduced by half. to produce a haploid gamete (meiosis). Meiosis produces four daughter cells of haploid by undergoing one round of DNA replication followed by two divisions. The homologous chromosomes are separated in the first division, and the chromatid sister is separated in the second division. Both cycles of cell division are used in the process of sexual reproduction at a point in its life cycle. Both are believed to be present in the last eukaryotic last ancestor.
Prokaryotes (bacteria) undergo vegetative cell division known as binary division, where their genetic material is separated into two daughter cells. All cell division, regardless of organism, is preceded by one round of DNA replication.
For simple unicellular microorganisms such as amoeba, a cell division is equivalent to reproduction - all new organisms are made. On a larger scale, mitotic cell division can create offspring of multicellular organisms, such as plants that grow from cuttings. Mitotic cell division enables sexually reproducing organisms to develop from a one-cell zygote, which is itself produced by meiotic cell division from the gametes. After growth, cell division by mitosis allows for the construction and improvement of sustainable organisms. The human body experiences about 10 quadrillion cell divisions for life.
The main concern of cell division is the maintenance of the original cell genome. Before division can occur, the genome information stored on the chromosome must be replicated, and the duplicated genome must be separated cleanly between cells. A lot of mobile infrastructure is involved in keeping genomic information consistent across generations.
Video Cell division
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Interphase
Interphase is a process that cells must pass before mitosis, meiosis, and cytokinesis. Interphase consists of four main stages: G1, S, G0, and G2. G1 is the time of cell growth. If the cell does not progress through G1, the cell then enters a stage called G0. In G0, the cells are alive but they are being held. The cells can then be recalled to the interfase if needed later. There are checkpoints during the interfase that allow the cell to develop or be denied further development. In phase S, the chromosomes are replicated so that the genetic content is maintained. During G2, the cell undergoes the final stage of growth before entering phase M. Phase M, may be mitosis or meiosis depending on the cell type. The germ cells undergo meiosis, while somatic cells will undergo mitosis. After the cell passes through phase M, it can then undergo cell division through cytokinesis. The control of each checkpoint is controlled by cyclin and cyclin dependent kinase. The development of interphase is the result of an increase in the number of cyclins. As the number of cyclins increases, more cyclins dependent kinase attaches to the cyclins that signal the cells further into the interphase. The cyclin peaks attached to the cyclin kinase depend on this system to push the cell out of the interphase and into phase M, where mitosis, meiosis, and cytokinesis occur.
Prophecy
Profase is the first stage of the division. Nuclear envelope is broken down, long strands of chromatin condense to form shorter visible strands called chromosomes, nucleolus disappears, and microtubules attached to chromosomes in kinetokores present in the centromere. Microtubules associated with the alignment and separation of chromosomes are referred to as spindle fibers and spindles. The chromosome will also be visible under a microscope and will be connected at the centromere. During this period of condensation and alignment, homologous chromosomes can exchange some of their DNA in a process known as a cross.
Metaphase
Metaphase is a stage in cell division when the chromosomes line up in the middle of a cell by the MTOC (the organizing center of microtubules) by pushing and pulling the centromeres from both chromatids which cause the chromosomes to move to the center. The chromosome is still condensed and is currently one step further than the most circular and thick. spindle fiber and is already connected to kinetochores. At this point, the ready chromosomes are split into opposite poles from the cell to the connected shaft.
Anafase
Anaphase is a very short stage of the cell cycle and occurs after chromosomes are paralleled in mitotic plates. Once the chromosomes are marching in the center of the cell, the spindle fibers will separate them. The chromosomes are split when the sister chromatid moves to the opposite side of the cell.
Telophase
Telophase is the last stage of the cell cycle. Two cells are formed around the chromatin in the two poles of the cell. The two nuclear membranes start to change and chromatin begins to free.
Maps Cell division
Variant
Cell is broadly classified into two main categories: simple and non-core prokaryotic cells, and complex nucleated eukaryotic cells. Due to their structural differences, eukaryotic and prokaryotic cells do not divide in the same way. Also, the pattern of cell division that converts eukaryotic stem cells into gametes (sperm cells in males or eggs in women), called meiosis, differs from the division of somatic cells in the body.
Degradation
Multicellular organisms replace obsolete cells through cell division. But in some animals, cell division eventually stops. In humans this happens, on average, after 52 divisions, known as the Hayflick limit. The cell is then referred to as senescent. Cells stop dividing by telomere, the protective DNA bits at the end of the chromosome required for replication, shortening with each copy, are eventually consumed. Cancer cells, on the other hand, are not considered to decrease in this way, if at all. An enzyme called telomerase, present in large quantities in cancer cells, rebuilds telomeres, enabling the division to continue indefinitely.
History
Cell division under the microscope was first discovered by the German botanist Hugo von Mohl in 1835 when he worked in the green algae Cladophora glomerata .
In 1943, the cell division was filmed for the first time, by Kurt Michelwith, using a contrast phase microscope.
See also
- Binary fission
- Cell growth
- A labile cell, a cell that continues to divide
- Klerokinesis
References
Further reading
- Morgan HI. (2007). "The Cell Cycle: Principles of Control" London: The New Science Press.
- J.M.Turner Fetus into Man (1978, 1989). Harvard University Press. ISBN 0-674-30692-9
- Cell division: binary fission and mitosis
External links
- How Cell Divide: Mitosis vs Meiosis
- The Mitosis Control and Cycle Control section of the Landmark Papers in Cell Biology (Gall JG, McIntosh JR, eds.) contains comments and links to a seminal research paper on mitosis and cell division. Published online in Pictures & amp; American Society for Cell Biology Video Library
- Images & amp; The American Society for Cell Biology Video Library contains many videos that show the division of cells.
- Cells Library Cell Division
- The video of the first cell division in the Xenopus laevis embryo (side view and top view), obtained by MRI (DOI of paper)
- Picture: Calanthe discolor Lindl. - Flavon Secret Flower Park
- Tyson cell division model and Description of the BioModels Database
- WormWeb.org: Interactive Visualization of C. elegans Cell Lineage - Visualize the entire set of nematode cell divisions C. elegans
Source of the article : Wikipedia
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