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Karyorelictea
Karyorelictea is a class of ciliates in the subphylum Postciliodesmatophora. Most species are members of the microbenthos community, that is, microscopic organisms found in the marine interstitial habitat, though one genus, '' Loxodes'', is found in freshwater. The majority of karyorelict taxa have not been cultivated in the laboratory, although clonal lines of '' Loxodes'' have been developed. Systematics According to Lynn (2008), the Karyorelictea class is divided into three orders: * Loxodida, containing the families Cryptopharyngidae and Loxodidae; * Protoheterotrichida, containing the families Aveliidae and Geleiidae; * Protostomatida, containing the families Kentrophoridae and Trachelocercidae. These three orders were defined morphologically, and have been confirmed with molecular phylogenetics. An additional family, Wilbertomorphidae, is of uncertain affiliation and has not been assigned to an order. Nuclear dimorphism All ciliates, including karyorelicteans ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Loxodes
''Loxodes'' is a genus of karyorelictean ciliates, belonging to family Loxodidae. It is the only known karyorelictean ciliate that lives in freshwater habitats. The term ''Loxodes'' derives from the ancient greek (), meaning "oblique, tilted". Ecology ''Loxodes'' lives in freshwater habitats such as lakes and ponds, unlike other karyorelictean ciliates such as the other loxodid genus '' Remanella'', which live in brackish-water or marine habitats. They feed on bacteria and protists such as microalgae. It is microaerobic, preferring low concentrations of oxygen, below 5% atmospheric saturation. It can also survive extended periods in anoxic water, where oxygen is absent. Under such conditions, ''Loxodes'' is able to use nitrate instead of oxygen as an electron acceptor for respiration. Nitrate respiration is rare among eukaryotes, and ''Loxodes'' was the first eukaryote known to have this capability. ''Loxodes'' is also sensitive to light. Geotaxis Both genera in the fami ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wilbertomorphidae
Wilbertomorphidae is a family of karyorelictean ciliates. The family is monotypic, because it contains a single genus ''Wilbertomorpha'' with a single known species, ''Wilbertomorpha colpoda''. Like most karyorelicteans, ''Wilbertomorpha'' lives in the marine interstitial habitat, between sediment grains. The cells are oval-shaped and about 45 µm long by 15 µm wide. Its distinctive features are a reduced oral apparatus ("mouth") and colorless granules of different shapes (rod-, cross-, and oval-shaped) in the cortex of the cell. Its phylogenetic relationship to other families of karyorelictean ciliates is unclear, because its morphology (ciliature) most closely resembles the order Loxodida, whereas molecular phylogenetics places it closer to the family Geleiidae Geleiidae is a family of karyorelict ciliates. It is sometimes synonymized with family Aveliidae. Geleiidae are very large ciliates (200–5000 µm), with a cylindrical shape, and a thinner, often be ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kentrophoridae
''Kentrophoros'' is a genus of ciliates in the class Karyorelictea. Ciliates in this genus lack a distinct oral apparatus and depend primarily on symbiotic bacteria for their nutrition. Systematics ''Kentrophoros'' is the sole genus in the family Kentrophoridae Jankowski 1980. The type species of the genus is ''K. fasciolatus'' Sauerbrey 1928, first described from the Bay of Kiel. Synonyms are ''Centrophorus'' Kahl 1931 (an illegitimate synonym because the name was already used for a genus of sharks) and ''Centrophorella'' Kahl 1935. Fifteen species of ''Kentrophoros'' have been formally described, although several of these names may be synonyms for the same species. Description The ciliates are long and ribbon-shaped, like other karyorelictean ciliates that live in the marine interstitial habitat. In some species, the cell body is folded or involuted into a tube or more elaborate shapes. The ventral side is ciliated, while the dorsal side is mostly unciliated except fo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
World Register Of Marine Species
The World Register of Marine Species (WoRMS) is a taxonomic database that aims to provide an authoritative and comprehensive list of names of marine organisms. Content The content of the registry is edited and maintained by scientific specialists on each group of organism. These taxonomists control the quality of the information, which is gathered from the primary scientific literature as well as from some external regional and taxon-specific databases. WoRMS maintains valid names of all marine organisms, but also provides information on synonyms and invalid names. It is an ongoing task to maintain the registry, since new species are constantly being discovered and described by scientists; in addition, the nomenclature and taxonomy of existing species is often corrected or changed as new research is constantly being published. Subsets of WoRMS content are made available, and can have separate badging and their own home/launch pages, as "subregisters", such as the ''World List ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cell Nucleus
The cell nucleus (pl. nuclei; from Latin or , meaning ''kernel'' or ''seed'') is a membrane-bound organelle found in eukaryotic cells. Eukaryotic cells usually have a single nucleus, but a few cell types, such as mammalian red blood cells, have no nuclei, and a few others including osteoclasts have many. The main structures making up the nucleus are the nuclear envelope, a double membrane that encloses the entire organelle and isolates its contents from the cellular cytoplasm; and the nuclear matrix, a network within the nucleus that adds mechanical support. The cell nucleus contains nearly all of the cell's genome. Nuclear DNA is often organized into multiple chromosomes – long stands of DNA dotted with various proteins, such as histones, that protect and organize the DNA. The genes within these chromosomes are structured in such a way to promote cell function. The nucleus maintains the integrity of genes and controls the activities of the cell by regulating g ... [...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] |
Somatic (biology)
The term somatic - etymologically from the Ancient Greek words of "σωματικός" (sōmatikós, “bodily”) and σῶμα (sôma, “body”) - is often used in biology to refer to the cells of the body in contrast to the reproductive (germline) cells, which usually give rise to the egg or sperm (or other gametes in other organisms). These somatic cells are diploid, containing two copies of each chromosome, whereas germ cells are haploid, as they only contain one copy of each chromosome (in preparation for fertilisation). Although under normal circumstances all somatic cells in an organism contain identical DNA, they develop a variety of tissue-specific characteristics. This process is called differentiation, through epigenetic and regulatory alterations. The grouping of similar cells and tissues creates the foundation for organs. Somatic mutations are changes to the genetics of a multicellular organism that are not passed on to its offspring through the germline. Most ca ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Transcription (biology)
Transcription is the process of copying a segment of DNA into RNA. The segments of DNA transcribed into RNA molecules that can encode proteins are said to produce messenger RNA (mRNA). Other segments of DNA are copied into RNA molecules called non-coding RNAs (ncRNAs). mRNA comprises only 1–3% of total RNA samples. Less than 2% of the human genome can be transcribed into mRNA ( Human genome#Coding vs. noncoding DNA), while at least 80% of mammalian genomic DNA can be actively transcribed (in one or more types of cells), with the majority of this 80% considered to be ncRNA. Both DNA and RNA are nucleic acids, which use base pairs of nucleotides as a complementary language. During transcription, a DNA sequence is read by an RNA polymerase, which produces a complementary, antiparallel RNA strand called a primary transcript. Transcription proceeds in the following general steps: # RNA polymerase, together with one or more general transcription factors, binds to promoter ... [...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] |
Germline
In biology and genetics, the germline is the population of a multicellular organism's cells that pass on their genetic material to the progeny (offspring). In other words, they are the cells that form the egg, sperm and the fertilised egg. They are usually differentiated to perform this function and segregated in a specific place away from other bodily cells. As a rule, this passing-on happens via a process of sexual reproduction; typically it is a process that includes systematic changes to the genetic material, changes that arise during recombination, meiosis and fertilization for example. However, there are many exceptions across multicellular organisms, including processes and concepts such as various forms of apomixis, autogamy, automixis, cloning or parthenogenesis. The cells of the germline are called germ cells. For example, gametes such as a sperm and an egg are germ cells. So are the cells that divide to produce gametes, called gametocytes, the cells that produce ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Molecular Phylogenetics
Molecular phylogenetics () is the branch of phylogeny that analyzes genetic, hereditary molecular differences, predominantly in DNA sequences, to gain information on an organism's evolutionary relationships. From these analyses, it is possible to determine the processes by which diversity among species has been achieved. The result of a molecular phylogenetic analysis is expressed in a phylogenetic tree. Molecular phylogenetics is one aspect of molecular systematics, a broader term that also includes the use of molecular data in taxonomy and biogeography. Molecular phylogenetics and molecular evolution correlate. Molecular evolution is the process of selective changes (mutations) at a molecular level (genes, proteins, etc.) throughout various branches in the tree of life (evolution). Molecular phylogenetics makes inferences of the evolutionary relationships that arise due to molecular evolution and results in the construction of a phylogenetic tree. History The theoretical ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gamete
A gamete (; , ultimately ) is a haploid cell that fuses with another haploid cell during fertilization in organisms that reproduce sexually. Gametes are an organism's reproductive cells, also referred to as sex cells. In species that produce two morphologically distinct types of gametes, and in which each individual produces only one type, a female is any individual that produces the larger type of gamete—called an ovum— and a male produces the smaller type—called a sperm. Sperm cells or spermatozoa are small and motile due to the flagellum, a tail-shaped structure that allows the cell to propel and move. In contrast, each egg cell or ovum is relatively large and non-motile. In short a gamete is an egg cell (female gamete) or a sperm (male gamete). In animals, ova mature in the ovaries of females and sperm develop in the testes of males. During fertilization, a spermatozoon and ovum unite to form a new diploid organism. Gametes carry half the genetic information of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
