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Cell division is a process by which a cell, called the parent cell, divides into two or more cells, called daughter cells. The cell is the structural and functional unit of all known living Organisms It is the smallest unit of an organism that is classified as living and is often called Cell division is usually a small segment of a larger cell cycle. The cell cycle, or cell-division cycle, is the series of events that take place in a eukaryotic cell leading to its replication This type of cell division is known as mitosis, and leaves the daughter cell capable of dividing again. In another type of cell division present only in eukaryotes, called meiosis, a cell is permanently transformed into a gamete and cannot divide again until fertilization. In Biology or life science meiosis (pronounced my-oh-sis is a process of reductional division in which the number of chromosomes per cell is cut in half

For simple unicellular organisms such as the Amoeba, one cell division is equivalent to reproduces-- an entire new organism is created. A microorganism (also spelled micro organism or micro-organism and also called a microbe) is an Organism that is Microscopic (usually Amoeba (sometimes amœba or ameba, plural amoebae) is a Genus of Protozoa that moves Vegetative reproduction is a type of Asexual reproduction found in plants and is also called vegetative propagation or vegetative multiplication. On a larger scale, mitotic cell division can create progeny from multicellular organisms, such as plants that grow from cuttings. Cell division also enables sexually reproducing organisms to develop from the one-celled zygote, which itself was produced by cell division from gametes. The Evolution of sexual reproduction is a major puzzle The first Fossilized evidence of sexually reproducing Organisms is from Eukaryotes of the Stenian For other meanings see Zygote (disambiguation. A zygote (from Greek ζυγωτός zugōtos "joined" or "yoked" A gamete (from Ancient Greek γαμέτης; translated gamete = wife gametes = husband is a cell that fuses with another gamete And after growth, cell division allows for continual renewal and repair of the organism. [1] A human being's body experiences about 10,000 trillion cell divisions in a lifetime. [2]

The primary concern of cell division is the maintenance of the original cell's genome. In classical genetics the genome of a Diploid Organism including Eukarya refers to a full set of chromosomes or genes in a Gamete, thereby Before division can occur, the genomic information which is stored in chromosomes must be replicated, and the duplicated genome separated cleanly between cells. A chromosome is an organized structure of DNA and Protein that is found in cells. A great deal of cellular infrastructure is involved in keeping genomic information consistent between "generations".

Contents

Variants

Three types of cell division
Three types of cell division

Cells are classified into two categories: simple, non-nucleated prokaryotic cells, and complex, nucleated eukaryotic cells. The prokaryotes (proʊˈkærioʊts singular prokaryote /proʊˈkæriət/ are a group of Organisms that lack a Cell nucleus (= karyon or any other Animals Plants fungi, and Protists are eukaryotes (juːˈkærɪɒt or -oʊt Organisms whose cells are organized into complex By dint of their structural differences, eukaryotic and prokaryotic cells do not divide in the same way.

Furthermore, the pattern of cell division that transforms eukaryotic stem cells into gametes (sperm in males or ova in females) is different from that of eukaryotic somatic (non-germ) cells. Stem cells are cells found in most if not all multi-cellular Organisms. The term sperm is derived from the Greek word (σπέρμα sperma (meaning "seed" and refers to the male reproductive cells. "Somatic" redirects here for the musician known as Somatic see Hahn Rowe.

Prokaryotic cells

Main article: binary fission

Prokaryotic cells are generally much more simple in structure when compared to eukaryotic cells. Binary fission is the form of Asexual reproduction and Cell division used by Prokaryotic organisms (such as Bacteria or Archea) They contain non-membranous organelles, lack a cell nucleus, and have a simplistic genome: Prokaryotic genome is not enclosed within a membrane. In Cell biology, the nucleus (pl nuclei; from Latin la ''nucleus'' or la ''nuculeus'' "little nut" or kernel is a membrane-enclosed The genetic material is a single circular DNA and is contained in the Cytoplasm (only one circular chromosome of limited size). A chromosome is an organized structure of DNA and Protein that is found in cells. Therefore, prokaryotic cell division, a process known as binary fission, is fast. Binary fission is the form of Asexual reproduction and Cell division used by Prokaryotic organisms (such as Bacteria or Archea) The chromosome is duplicated prior to division. The two copies of the chromosome attach to opposing sides of the cellular membrane. Cytokinesis, the physical separation of the cell, occurs immediately. Cytokinesis is the process whereby the Cytoplasm of a single Eukaryotic cell is divided to form two daughter cells Prokaryotic cells, found only among bacteria and archaea (special kind of prokaryotes)[3], have a cell wall outside, the cell membrane and lack membrane bound organelles. Prokaryotes have only one copy of each gene and thus are haploid organisms. Prokaryotic genes are expressed in either moncistronic or polycistronic transcriptional units:Monocistronic units encode a single gene product or Polycistronic units allow the expression of multiple gene products. Messenger ribonucleic acid ( mRNA) is a molecule of RNA encoding a chemical "blueprint" for a Protein product

Eukaryotic cells

Eukaryotic cells consist of cell membrane, organelles which represent the functional components for storage, excretion, digestion and nucleus (centre of the cell), it contains all the vital information needed by the cell or the whole organism to function, grow and reproduce. Animals Plants fungi, and Protists are eukaryotes (juːˈkærɪɒt or -oʊt Organisms whose cells are organized into complex In Cell biology, an organelle (pronunciation /ɔː(rgəˡnɛl/ is a specialized subunit within a cell that has a specific function and is usually separately enclosed Excretion is the process of eliminating waste products of Metabolism and other non-useful materials Digestion is the breaking down of chemicals in the body into a form that can be absorbed Reproduction is the Biological process by which new individual Organisms are produced

Eukaryotic cells are found in humans, plants and animals, also algae, and protozoa. Algae ( sing. alga are a large and diverse group of simple typically Autotrophic organisms ranging from Unicellular to Multicellular forms Protozoa (in Greek πρῶτον proton "first" and ζῷα zoia "animals" are unicellular Eukaryotes (singular Eukaryotic cells have both a cellular membrane and a nuclear membrane. Eukaryotic genome is more complex than that of prokaryotes and distributed among multiple chromosomes. In classical genetics the genome of a Diploid Organism including Eukarya refers to a full set of chromosomes or genes in a Gamete, thereby The prokaryotes (proʊˈkærioʊts singular prokaryote /proʊˈkæriət/ are a group of Organisms that lack a Cell nucleus (= karyon or any other A chromosome is an organized structure of DNA and Protein that is found in cells.

Examples of cell division in multicellular eukariotic organisms include repair, growth, and development. An injury or wound is healed when the cells exposed by the injury divide at an excellerated rate until they come into contact with other cells. After this the cells return to a more typical division rate. Cell division causes an organism to grow as long as the rate of cell division exceeds normal cell death. As cells divide and become more numerous they are located in more diverse physical and chemical environments. These variations in local conditions influence the cells to alter gene expression causing the cells to differentiate and become more specialized allowing an organism to develop.

Degradation

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. Human beings, humans or man (Origin 1590–1600 L homō man OL hemō the earthly one (see Humus The Hayflick limit is the number of times a cell will divide before it stops due to the telomere reaching a critical length. The cell is then referred to as senescent. Senescence refers to the biological processes of a living Organism approaching an advanced age (i Senescent cells deteriorate and die, causing the body to age. Cells stop dividing because the telomeres, protective bits of DNA on the end of a chromosome, become shorter with each division and eventually can no longer protect the chromosome. A telomere is a region of repetitive DNA at the end of Chromosomes which protects the end of the chromosome from destruction A chromosome is an organized structure of DNA and Protein that is found in cells. Cancer cells, on the other hand, are immortal. Cancer (medical term Malignant Neoplasm) is a class of Diseases in which a group of cells display uncontrolled An enzyme called telomerase, present in large quantites in cancerous cells, rebuilds the telomeres, allowing division to continue indefinitely. Enzymes are Biomolecules that catalyze ( ie increase the rates of Chemical reactions Almost all enzymes are Proteins Telomerase is an Enzyme that adds specific DNA sequence repeats ("TTAGGG" in all vertebrates to the 3' ("three prime" end of DNA strands in the

See also

References

  1. Morgan DO. The cell cycle, or cell-division cycle, is the series of events that take place in a eukaryotic cell leading to its replication Mitosis is the process in which a Eukaryotic cell separates the Chromosomes in its Cell nucleus, into two identical sets in two daughter nuclei In Biology or life science meiosis (pronounced my-oh-sis is a process of reductional division in which the number of chromosomes per cell is cut in half Binary fission is the form of Asexual reproduction and Cell division used by Prokaryotic organisms (such as Bacteria or Archea) The term cell growth is used in two different ways in Biology. (2007) "The Cell Cycle: Principles of Control" London: New Science Press.
  2. J. M. Turner Fetus into Man (1978, 1989). Harvard University Press. ISBN 0-674-30692-9

Other references

  1. ^ Maton, Anthea; Hopkins, Jean Johnson, Susan LaHart, David, Quon Warner, David, Wright, Jill D (1997). Cells: Building Blocks of Life. New Jersey: Prentice Hall, 70-74. ISBN 0-13423476-6.  
  2. ^ Quammen, David (April 2008), “Contagious cancer: The evolution of a killer”, Harper's 316 (1895): 42 .
  3. ^ Robert F. Weaver. Posttranslation. In. Molecular Biology. Fourth Edition. Page 600McGraw-Hill International Edition. ISBN 978-0-07-110216-2

External links

The African clawed frog ( Xenopus laevis, also known as platanna) is a species of South African aquatic Frog of the genus Xenopus

Dictionary

cell division

-noun

  1. a process by which a cell divides into two cells
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