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Epigenetic Controls In Ciliates
Epigenetic controls in ciliates is about the unique characteristic of Ciliates, which is that they possess two kinds of nuclei (this phenomenon is called nuclear dimorphism): a micronucleus used for inheritance, and a macronucleus, which controls the metabolism. The micronucleus contains the entirety of the genome whereas the macronucleus only contains the DNA necessary for vegetative growth. The macronucleus divides via amitosis Amitosis ('' a-'' + ''mitosis''), also called karyostenosis or direct cell division or binary fission, is cell proliferation that does not occur by mitosis, the mechanism usually identified as essential for cell division in eukaryotes. The polyploi ..., whereas the micronucleus undergoes typical mitosis. During sexual development a new macronucleus is formed from the meiosis of the micronucleus, where the removal of transposons occurs. On the division or reproduction of ciliates, the two nuclei are under several epigenetic controls. References ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ciliates
The ciliates are a group of alveolates characterized by the presence of hair-like organelles called cilia, which are identical in structure to eukaryotic flagella, but are in general shorter and present in much larger numbers, with a different undulating pattern than flagella. Cilia occur in all members of the group (although the peculiar Suctoria only have them for part of their life cycle) and are variously used in swimming, crawling, attachment, feeding, and sensation. Ciliates are an important group of protists, common almost anywhere there is water—in lakes, ponds, oceans, rivers, and soils. About 4,500 unique free-living species have been described, and the potential number of extant species is estimated at 27,000–40,000. Included in this number are many ectosymbiotic and endosymbiotic species, as well as some obligate and opportunistic parasites. Ciliate species range in size from as little as 10 µm in some colpodeans to as much as 4 mm in length in some gel ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nuclear Dimorphism
Nuclear dimorphism is a term referred to the special characteristic of having two different kinds of nuclei in a cell. There are many differences between the types of nuclei. This feature is observed in protozoan ciliates, like ''Tetrahymena'', and some foraminifera. Ciliates contain two nucleus types: a macronucleus that is primarily used to control metabolism, and a micronucleus which performs reproductive functions and generates the macronucleus. The compositions of the nuclear pore complexes help determine the properties of the macronucleus and micronucleus. Nuclear dimorphism is subject to complex epigenetic controls. Nuclear dimorphism is continuously being studied to understand exactly how the mechanism works and how it is beneficial to cells. Learning about nuclear dimorphism is beneficial to understanding old eukaryotic mechanisms that have been preserved within these unicellular organisms but did not evolve into multicellular eukaryotes. Key components The ciliated p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Micronucleus
Micronucleus is the name given to the small nucleus that forms whenever a chromosome or a fragment of a chromosome is not incorporated into one of the daughter nuclei during cell division. It usually is a sign of genotoxic events and chromosomal instability. Micronuclei are commonly seen in cancerous cells and may indicate genomic damage events that can increase the risk of developmental or degenerative diseases. Micronuclei form during anaphase from lagging acentric chromosome or chromatid fragments caused by incorrectly repaired or unrepaired DNA breaks or by nondisjunction of chromosomes. This incorrect segregation of chromosomes may result from hypomethylation of repeat sequences present in pericentromeric DNA, irregularities in kinetochore proteins or their assembly, dysfunctional spindle apparatus, or flawed anaphase checkpoint genes. Micronuclei can contribute to genome instability by promoting a catastrophic mutational event called chromothripsis. Many micronucleus assays h ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Macronucleus
A macronucleus (formerly also meganucleus) is the larger type of nucleus in ciliates. Macronuclei are polyploid and undergo direct division without mitosis. It controls the non-reproductive cell functions, such as metabolism. During conjugation, the macronucleus disintegrates, and a new macronucleus is formed by karyogamy of the micronuclei. The macronucleus contains hundreds to thousands of chromosomes, each present in many copies. The macronucleus lacks a mechanism to precisely partition this complex genome equally during nuclear division; thus, how the cell manages to maintain a balanced genome after generations of divisions is unknown. See also *Micronucleus Micronucleus is the name given to the small nucleus that forms whenever a chromosome or a fragment of a chromosome is not incorporated into one of the daughter nuclei during cell division. It usually is a sign of genotoxic events and chromosomal i ... References . Cell nucleus Ciliate biology {{Cilia ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Metabolism
Metabolism (, from el, μεταβολή ''metabolē'', "change") is the set of life-sustaining chemical reactions in organisms. The three main functions of metabolism are: the conversion of the energy in food to energy available to run cellular processes; the conversion of food to building blocks for proteins, lipids, nucleic acids, and some carbohydrates; and the elimination of metabolic wastes. These enzyme-catalyzed reactions allow organisms to grow and reproduce, maintain their structures, and respond to their environments. The word metabolism can also refer to the sum of all chemical reactions that occur in living organisms, including digestion and the transportation of substances into and between different cells, in which case the above described set of reactions within the cells is called intermediary (or intermediate) metabolism. Metabolic reactions may be categorized as '' catabolic'' – the ''breaking down'' of compounds (for example, of glucose to pyruvate ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Amitosis
Amitosis ('' a-'' + ''mitosis''), also called karyostenosis or direct cell division or binary fission, is cell proliferation that does not occur by mitosis, the mechanism usually identified as essential for cell division in eukaryotes. The polyploid macronucleus found in ciliates divides amitotically. While normal mitosis results in a precise division of parental alleles, amitosis results in a random distribution of parental alleles. Ploidy levels of >1000 in some species means both parental alleles can be maintained over many generations, while species with fewer numbers of each chromosome will tend to become homozygous for one or the other parental allele through a process known as phenotypic or allelic assortment. It does not involve maximal condensation of chromatin into chromosomes, observable by light microscopy as they line up in pairs along the metaphase plate. It does not involve these paired structures being pulled in opposite directions by a mitotic spindle to form daug ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Transposons
A transposable element (TE, transposon, or jumping gene) is a nucleic acid sequence in DNA that can change its position within a genome, sometimes creating or reversing mutations and altering the cell's genetic identity and genome size. Transposition often results in duplication of the same genetic material. Barbara McClintock's discovery of them earned her a Nobel Prize in 1983. Its importance in personalized medicine is becoming increasingly relevant, as well as gaining more attention in data analytics given the difficulty of analysis in very high dimensional spaces. Transposable elements make up a large fraction of the genome and are responsible for much of the mass of DNA in a eukaryotic cell. Although TEs are selfish genetic elements, many are important in genome function and evolution. Transposons are also very useful to researchers as a means to alter DNA inside a living organism. There are at least two classes of TEs: Class I TEs or retrotransposons generally fu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ciliate Biology
The ciliates are a group of alveolates characterized by the presence of hair-like organelles called cilia, which are identical in structure to eukaryotic flagella, but are in general shorter and present in much larger numbers, with a different undulating pattern than flagella. Cilia occur in all members of the group (although the peculiar Suctoria only have them for part of their life cycle) and are variously used in swimming, crawling, attachment, feeding, and sensation. Ciliates are an important group of protists, common almost anywhere there is water—in lakes, ponds, oceans, rivers, and soils. About 4,500 unique free-living species have been described, and the potential number of extant species is estimated at 27,000–40,000. Included in this number are many ectosymbiotic and endosymbiotic species, as well as some obligate and opportunistic parasites. Ciliate species range in size from as little as 10 µm in some colpodeans to as much as 4 mm in length in some gel ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
