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Cytokinesis Illustration
Cytokinesis () is the part of the cell division process during which the cytoplasm of a single eukaryotic cell divides into two daughter cells. Cytoplasmic division begins during or after the late stages of nuclear division in mitosis and meiosis. During cytokinesis the spindle apparatus partitions and transports duplicated chromatids into the cytoplasm of the separating daughter cells. It thereby ensures that chromosome number and complement are maintained from one generation to the next and that, except in special cases, the daughter cells will be functional copies of the parent cell. After the completion of the telophase and cytokinesis, each daughter cell enters the interphase of the cell cycle. Particular functions demand various deviations from the process of symmetrical cytokinesis; for example in oogenesis in animals the ovum takes almost all the cytoplasm and organelles. This leaves very little for the resulting polar bodies, which in most species die without function, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polar Bodies
A polar body is a small haploid cell that is formed at the same time as an egg cell during oogenesis, but generally does not have the ability to be fertilized. It is named from its polar position in the egg. When certain diploid cells in animals undergo cytokinesis after meiosis to produce egg cells, they sometimes divide unevenly. Most of the cytoplasm is segregated into one daughter cell, which becomes the egg or ovum, while the smaller ''polar bodies'' only get a small amount of cytoplasm. They frequently die and disintegrate by apoptosis, but in some cases remain and can be important in the life cycle of the organism. Twinning ''Polar body twinning'' is a hypothesized form of twinning in meiosis, where one or more polar bodies do not disintegrate and are fertilized by sperm. Twinning would occur, in principle, if the egg cell and a polar body were both fertilized by separate sperms. However, even if fertilization occurs, further development would usually not occur becaus ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Classical Compound
Neoclassical compounds are compound words composed from combining forms (which act as affixes or stems) derived from classical Latin or ancient Greek roots. New Latin comprises many such words and is a substantial component of the technical and scientific lexicon of English and other languages, via international scientific vocabulary (ISV). For example, ''bio-'' combines with '' -graphy'' to form ''biography'' ("life" + "writing/recording"). Source of international technical vocabulary Neoclassical compounds represent a significant source of Neo-Latin vocabulary. Moreover, since these words are composed from classical languages whose prestige is or was respected throughout the Western European culture, these words typically appear in many different languages. Their widespread use makes technical writing generally accessible to readers who may only have a smattering of the language in which it appears. Not all European languages have been equally receptive to neoclassical ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oxford University Press
Oxford University Press (OUP) is the university press of the University of Oxford. It is the largest university press in the world, and its printing history dates back to the 1480s. Having been officially granted the legal right to print books by decree in 1586, it is the second oldest university press after Cambridge University Press. It is a department of the University of Oxford and is governed by a group of 15 academics known as the Delegates of the Press, who are appointed by the vice-chancellor of the University of Oxford. The Delegates of the Press are led by the Secretary to the Delegates, who serves as OUP's chief executive and as its major representative on other university bodies. Oxford University Press has had a similar governance structure since the 17th century. The press is located on Walton Street, Oxford, opposite Somerville College, in the inner suburb of Jericho. For the last 500 years, OUP has primarily focused on the publication of pedagogical texts a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lexico
Lexico was a dictionary website that provided a collection of English and Spanish dictionaries produced by Oxford University Press (OUP), the publishing house of the University of Oxford. While the dictionary content on Lexico came from OUP, this website was operated by Dictionary.com, whose eponymous website hosts dictionaries by other publishers such as Random House. The website was closed and redirected to Dictionary.com on 26 August 2022. Before the Lexico site was launched, the ''Oxford Dictionary of English'' and ''New Oxford American Dictionary'' were hosted by OUP's own website Oxford Dictionaries Online (ODO), later known as Oxford Living Dictionaries. The dictionaries' definitions have also appeared in Google Dictionary, Google definition search and the Dictionary (software), Dictionary application on macOS, among others, licensed through the Oxford Dictionaries application programming interface, API. History In the 2000s, OUP allowed access to content of the ''Compac ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Anaphase
Anaphase () is the stage of mitosis after the process of metaphase, when replicated chromosomes are split and the newly-copied chromosomes (daughter chromatids) are moved to opposite poles of the cell. Chromosomes also reach their overall maximum condensation in late anaphase, to help chromosome segregation and the re-formation of the nucleus. Anaphase starts when the anaphase promoting complex marks an inhibitory chaperone called securin for destruction by ubiquinylating it. Securin is a protein which inhibits a protease known as separase. The destruction of securin unleashes separase which then breaks down cohesin, a protein responsible for holding sister chromatids together. At this point, three subclasses of microtubule unique to mitosis are involved in creating the forces necessary to separate the chromatids: kinetochore microtubules, interpolar microtubules, and astral microtubules. The centromeres are split, and the sister chromatids are pulled toward the poles ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Linear Chromosome
A linear chromosome is a chromosome which is linear in shape, and contains terminal ends. In most eukaryotic cells, DNA is arranged in multiple linear chromosomes. In contrast, most prokaryotic cells generally contain a singular circular chromosome. However, linear chromosomes are not limited to eukaryotic organisms; some prokaryotic organisms have linear chromosomes as well, such as ''Borrelia burgdorferi''. In fact, experiments in which the circular chromosomes of prokaryotic organisms have been linearized have demonstrated that some prokaryotes can maintain viability even with linear chromosomes. In general, the factors which led to the evolution of linear chromosomes in eukaryotes are not well understood. One potential selective pressure in favor of linear chromosomes relates to the size of an organism's genome: linear chromosomes may make transcription and replication of large genomes easier. In an organism with a very large genome, circular chromosomes could potentially cause ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Circular Chromosome
A circular chromosome is a chromosome in bacteria, archaea, mitochondria, and chloroplasts, in the form of a molecule of circular DNA, unlike the linear chromosome of most eukaryotes. Most prokaryote chromosomes contain a circular DNA molecule – there are no free ends to the DNA. Free ends would otherwise create significant challenges to cells with respect to DNA replication and stability. Cells that do contain chromosomes with DNA ends, or telomeres (most eukaryotes), have acquired elaborate mechanisms to overcome these challenges. However, a circular chromosome can provide other challenges for cells. After replication, the two progeny circular chromosomes can sometimes remain interlinked or tangled, and they must be resolved so that each cell inherits one complete copy of the chromosome during cell division. Replication The circular bacteria chromosome replication is best understood in the well-studied bacteria ''Escherichia coli'' and ''Bacillus subtilis''. Chromosom ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Binary Fission
Binary may refer to: Science and technology Mathematics * Binary number, a representation of numbers using only two digits (0 and 1) * Binary function, a function that takes two arguments * Binary operation, a mathematical operation that takes two arguments * Binary relation, a relation involving two elements * Binary-coded decimal, a method for encoding for decimal digits in binary sequences * Finger binary, a system for counting in binary numbers on the fingers of human hands Computing * Binary code, the digital representation of text and data * Bit, or binary digit, the basic unit of information in computers * Binary file, composed of something other than human-readable text ** Executable, a type of binary file that contains machine code for the computer to execute * Binary tree, a computer tree data structure in which each node has at most two children Astronomy * Binary star, a star system with two stars in it * Binary planet, two planetary bodies of comparabl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Prokaryote
A prokaryote () is a single-celled organism that lacks a nucleus and other membrane-bound organelles. The word ''prokaryote'' comes from the Greek πρό (, 'before') and κάρυον (, 'nut' or 'kernel').Campbell, N. "Biology:Concepts & Connections". Pearson Education. San Francisco: 2003. In the two-empire system arising from the work of Édouard Chatton, prokaryotes were classified within the empire Prokaryota. But in the three-domain system, based upon molecular analysis, prokaryotes are divided into two domains: ''Bacteria'' (formerly Eubacteria) and '' Archaea'' (formerly Archaebacteria). Organisms with nuclei are placed in a third domain, Eukaryota. In the study of the origins of life, prokaryotes are thought to have arisen before eukaryotes. Besides the absence of a nucleus, prokaryotes also lack mitochondria, or most of the other membrane-bound organelles that characterize the eukaryotic cell. It was once thought that prokaryotic cellular components within the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cell Wall
A cell wall is a structural layer surrounding some types of cells, just outside the cell membrane. It can be tough, flexible, and sometimes rigid. It provides the cell with both structural support and protection, and also acts as a filtering mechanism. Cell walls are absent in many eukaryotes, including animals, but are present in some other ones like fungi, algae and plants, and in most prokaryotes (except mollicute bacteria). A major function is to act as pressure vessels, preventing over-expansion of the cell when water enters. The composition of cell walls varies between taxonomic group and species and may depend on cell type and developmental stage. The primary cell wall of land plants is composed of the polysaccharides cellulose, hemicelluloses and pectin. Often, other polymers such as lignin, suberin or cutin are anchored to or embedded in plant cell walls. Algae possess cell walls made of glycoproteins and polysaccharides such as carrageenan and agar that are ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cell Plate
image:Phragmoplast.png, 300px, Phragmoplast and cell plate formation in a plant cell during cytokinesis. Left side: Phragmoplast forms and cell plate starts to assemble in the center of the cell. Towards the right: Phragmoplast enlarges in a donut-shape towards the outside of the cell, leaving behind mature cell plate in the center. The cell plate will transform into the new cell wall once cytokinesis is complete. Cytokinesis in embryophyte, terrestrial plants occurs by cell plate formation. This process entails the delivery of Golgi-derived and endosomal vesicles carrying [ell wall and cell membrane components to the plane of cell division and the subsequent fusion of these vesicles within this plate. After formation of an early tubulo-vesicular network at the center of the cell, the initially labile cell plate consolidates into a tubular network and eventually a fenestrated sheet. The cell plate grows outward from the center of the cell to the parental plasma membrane with which ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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