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84-541: Barbus is a genus of ray-finned fish in the family Cyprinidae . The type species of Barbus is the common barbel , first described as Cyprinus barbus and now named Barbus barbus . Barbus is the namesake genus of the subfamily Barbinae, but given their relationships, that taxon is better included in the Cyprininae at least for the largest part (including the type species of Barbus ). Their common names – barbs and barbels – refer to

168-409: A Pneumocystis carinii infection, which indicates a weak immune system. Triploidy may be the result of either digyny (the extra haploid set is from the mother) or diandry (the extra haploid set is from the father). Diandry is mostly caused by reduplication of the paternal haploid set from a single sperm, but may also be the consequence of dispermic (two sperm) fertilization of the egg. Digyny

252-636: A hybrid genome with two sets of chromosomes derived from Triticum urartu and two sets of chromosomes derived from Aegilops speltoides . Each chromosome pair derived from the Triticum urartu parent is homoeologous to the opposite chromosome pair derived from the Aegilops speltoides parent, though each chromosome pair unto itself is homologous . Examples in animals are more common in non-vertebrates such as flatworms , leeches , and brine shrimp . Within vertebrates, examples of stable polyploidy include

336-410: A miscarriage ; those that do survive to term typically die shortly after birth. In some cases, survival past birth may be extended if there is mixoploidy with both a diploid and a triploid cell population present. There has been one report of a child surviving to the age of seven months with complete triploidy syndrome. He failed to exhibit normal mental or physical neonatal development, and died from

420-407: A genus is determined by taxonomists . The standards for genus classification are not strictly codified, so different authorities often produce different classifications for genera. There are some general practices used, however, including the idea that a newly defined genus should fulfill these three criteria to be descriptively useful: Moreover, genera should be composed of phylogenetic units of

504-651: A later homonym of a validly published name is a nomen illegitimum or nom. illeg. ; for a full list refer to the International Code of Nomenclature for algae, fungi, and plants and the work cited above by Hawksworth, 2010. In place of the "valid taxon" in zoology, the nearest equivalent in botany is " correct name " or "current name" which can, again, differ or change with alternative taxonomic treatments or new information that results in previously accepted genera being combined or split. Prokaryote and virus codes of nomenclature also exist which serve as

588-628: A long time and redescribed as new by a range of subsequent workers, or if a range of genera previously considered separate taxa have subsequently been consolidated into one. For example, the World Register of Marine Species presently lists 8 genus-level synonyms for the sperm whale genus Physeter Linnaeus, 1758, and 13 for the bivalve genus Pecten O.F. Müller, 1776. Within the same kingdom, one generic name can apply to one genus only. However, many names have been assigned (usually unintentionally) to two or more different genera. For example,

672-852: A mechanism for a kind of 'reverse speciation', whereby gene flow is enabled following the polyploidy event, even between lineages that previously experienced no gene flow as diploids. This has been detailed at the genomic level in Arabidopsis arenosa and Arabidopsis lyrata . Each of these species experienced independent autopolyploidy events (within-species polyploidy, described below), which then enabled subsequent interspecies gene flow of adaptive alleles, in this case stabilising each young polyploid lineage. Such polyploidy-enabled adaptive introgression may allow polyploids at act as 'allelic sponges', whereby they accumulate cryptic genomic variation that may be recruited upon encountering later environmental challenges. Polyploid types are labeled according to

756-481: A more common path to allopolyploidy because F 1 hybrids between taxa often have relatively high rates of unreduced gamete formation – divergence between the genomes of the two taxa result in abnormal pairing between homoeologous chromosomes or nondisjunction during meiosis. In this case, allopolyploidy can actually restore normal, bivalent meiotic pairing by providing each homoeologous chromosome with its own homologue. If divergence between homoeologous chromosomes

840-403: A paleopolyploid. It is a middle aged polyploid. Often this refers to whole genome duplication followed by intermediate levels of diploidization. Ancient genome duplications probably occurred in the evolutionary history of all life. Duplication events that occurred long ago in the history of various evolutionary lineages can be difficult to detect because of subsequent diploidization (such that

924-695: A polyploid starts to behave cytogenetically as a diploid over time) as mutations and gene translations gradually make one copy of each chromosome unlike the other copy. Over time, it is also common for duplicated copies of genes to accumulate mutations and become inactive pseudogenes. In many cases, these events can be inferred only through comparing sequenced genomes . Examples of unexpected but recently confirmed ancient genome duplications include baker's yeast ( Saccharomyces cerevisiae ), mustard weed/thale cress ( Arabidopsis thaliana ), rice ( Oryza sativa ), and two rounds of whole genome duplication (the 2R hypothesis ) in an early evolutionary ancestor of

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1008-409: A reference for designating currently accepted genus names as opposed to others which may be either reduced to synonymy, or, in the case of prokaryotes, relegated to a status of "names without standing in prokaryotic nomenclature". An available (zoological) or validly published (botanical) name that has been historically applied to a genus but is not regarded as the accepted (current/valid) name for

1092-598: A sterile triploid hybrid between E. guttata and E. lutea, both of which have been introduced and naturalised in the United Kingdom. New populations of E. peregrina arose on the Scottish mainland and the Orkney Islands via genome duplication from local populations of E. × robertsii . Because of a rare genetic mutation, E. peregrina is not sterile. On the other hand, polyploidization can also be

1176-427: A taxon; however, the names published in suppressed works are made unavailable via the relevant Opinion dealing with the work in question. In botany, similar concepts exist but with different labels. The botanical equivalent of zoology's "available name" is a validly published name . An invalidly published name is a nomen invalidum or nom. inval. ; a rejected name is a nomen rejiciendum or nom. rej. ;

1260-455: A total of c. 520,000 published names (including synonyms) as at end 2019, increasing at some 2,500 published generic names per year. "Official" registers of taxon names at all ranks, including genera, exist for a few groups only such as viruses and prokaryotes, while for others there are compendia with no "official" standing such as Index Fungorum for fungi, Index Nominum Algarum and AlgaeBase for algae, Index Nominum Genericorum and

1344-777: A whole, the genus is not yet as well represented in aquaria as the Southeast Asian Puntius . Barbus has a long history as a " wastebasket taxon ". Historically, most fish commonly known as " barbs " were usually placed here by default. More recently, many "barbs" have been reclassified into genera such as Arabibarbus , Barbichthys , Barbodes , Barboides , Barbonymus , Barbopsis , Caecobarbus , Capoeta , Carasobarbus , Clypeobarbus , Enteromius , Hypselobarbus , Hypsibarbus , Labeobarbus , Leptobarbus , Luciobarbus , Mesopotamichthys , Poropuntius , Probarbus , Pseudobarbus , Puntioplites and Puntius . Thus, Barbus

1428-407: Is common among ferns and flowering plants (see Hibiscus rosa-sinensis ), including both wild and cultivated species . Wheat , for example, after millennia of hybridization and modification by humans, has strains that are diploid (two sets of chromosomes), tetraploid (four sets of chromosomes) with the common name of durum or macaroni wheat, and hexaploid (six sets of chromosomes) with

1512-612: Is discouraged by both the International Code of Zoological Nomenclature and the International Code of Nomenclature for algae, fungi, and plants , there are some five thousand such names in use in more than one kingdom. For instance, A list of generic homonyms (with their authorities), including both available (validly published) and selected unavailable names, has been compiled by the Interim Register of Marine and Nonmarine Genera (IRMNG). The type genus forms

1596-446: Is dotted by past and recent whole-genome duplication events (see Albertin and Marullo 2012 for review). Several examples of polyploids are known: In addition, polyploidy is frequently associated with hybridization and reticulate evolution that appear to be highly prevalent in several fungal taxa. Indeed, homoploid speciation (hybrid speciation without a change in chromosome number) has been evidenced for some fungal species (such as

1680-698: Is even across the two subgenomes, this can theoretically result in rapid restoration of bivalent pairing and disomic inheritance following allopolyploidization. However multivalent pairing is common in many recently formed allopolyploids, so it is likely that the majority of meiotic stabilization occurs gradually through selection. Because pairing between homoeologous chromosomes is rare in established allopolyploids, they may benefit from fixed heterozygosity of homoeologous alleles. In certain cases, such heterozygosity can have beneficial heterotic effects, either in terms of fitness in natural contexts or desirable traits in agricultural contexts. This could partially explain

1764-684: Is for the time being restricted to typical barbels, and only contains fishes from Africa and Europe , as well as adjacent Asia . However, the genus even in the reduced version is probably paraphyletic , and many African species (particularly the small ones) do not seem to belong here, either. Eventually, Barbus is likely to be restricted to the group around B. barbus – the large European to Ponto-Caspian species commonly known as "barbels". Luciobarbus and particularly Messinobarbus are highly similar and might better be included in Barbus again. They all seem to be close relatives – perhaps

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1848-885: Is frequent in plants, some estimates suggesting that 30–80% of living plant species are polyploid, and many lineages show evidence of ancient polyploidy ( paleopolyploidy ) in their genomes. Huge explosions in angiosperm species diversity appear to have coincided with the timing of ancient genome duplications shared by many species. It has been established that 15% of angiosperm and 31% of fern speciation events are accompanied by ploidy increase. Polyploid plants can arise spontaneously in nature by several mechanisms, including meiotic or mitotic failures, and fusion of unreduced (2 n ) gametes. Both autopolyploids (e.g. potato ) and allopolyploids (such as canola, wheat and cotton) can be found among both wild and domesticated plant species. Most polyploids display novel variation or morphologies relative to their parental species, that may contribute to

1932-495: Is haploid, and produces gametes by mitosis ; the sporophyte generation is diploid and produces spores by meiosis . Polyploidy is the result of whole-genome duplication during the evolution of species. It may occur due to abnormal cell division , either during mitosis, or more commonly from the failure of chromosomes to separate during meiosis or from the fertilization of an egg by more than one sperm. In addition, it can be induced in plants and cell cultures by some chemicals:

2016-514: Is more rarely diagnosed than triploidy, but is observed in 1–2% of early miscarriages. However, some tetraploid cells are commonly found in chromosome analysis at prenatal diagnosis and these are generally considered 'harmless'. It is not clear whether these tetraploid cells simply tend to arise during in vitro cell culture or whether they are also present in placental cells in vivo . There are, at any rate, very few clinical reports of fetuses/infants diagnosed with tetraploidy mosaicism. Mixoploidy

2100-473: Is most commonly caused by either failure of one meiotic division during oogenesis leading to a diploid oocyte or failure to extrude one polar body from the oocyte . Diandry appears to predominate among early miscarriages , while digyny predominates among triploid zygotes that survive into the fetal period. However, among early miscarriages, digyny is also more common in those cases less than 8 + 1 ⁄ 2 weeks gestational age or those in which an embryo

2184-433: Is most commonly induced by treating seeds with the chemical colchicine . Some crops are found in a variety of ploidies: tulips and lilies are commonly found as both diploid and triploid; daylilies ( Hemerocallis cultivars) are available as either diploid or tetraploid; apples and kinnow mandarins can be diploid, triploid, or tetraploid. Besides plants and animals, the evolutionary history of various fungal species

2268-623: Is often associated with apomictic mating systems. In agricultural systems, autotriploidy can result in seedlessness, as in watermelons and bananas . Triploidy is also utilized in salmon and trout farming to induce sterility. Rarely, autopolyploids arise from spontaneous, somatic genome doubling, which has been observed in apple ( Malus domesticus ) bud sports . This is also the most common pathway of artificially induced polyploidy, where methods such as protoplast fusion or treatment with colchicine , oryzalin or mitotic inhibitors are used to disrupt normal mitotic division, which results in

2352-440: Is part of cytology and, more specifically, cytogenetics . Although the replication and transcription of DNA is highly standardized in eukaryotes , the same cannot be said for their karyotypes, which are highly variable between species in chromosome number and in detailed organization despite being constructed out of the same macromolecules. In some cases, there is even significant variation within species. This variation provides

2436-435: Is present. There are also two distinct phenotypes in triploid placentas and fetuses that are dependent on the origin of the extra haploid set. In digyny, there is typically an asymmetric poorly grown fetus , with marked adrenal hypoplasia and a very small placenta . In diandry, a partial hydatidiform mole develops. These parent-of-origin effects reflect the effects of genomic imprinting . Complete tetraploidy

2520-412: Is quite commonly observed in human preimplantation embryos and includes haploid/diploid as well as diploid/tetraploid mixed cell populations. It is unknown whether these embryos fail to implant and are therefore rarely detected in ongoing pregnancies or if there is simply a selective process favoring the diploid cells. A polyploidy event occurred within the stem lineage of the teleost fish. Polyploidy

2604-460: Is somewhat arbitrary. Although all species within a genus are supposed to be "similar", there are no objective criteria for grouping species into genera. There is much debate among zoologists about whether enormous, species-rich genera should be maintained, as it is extremely difficult to come up with identification keys or even character sets that distinguish all species. Hence, many taxonomists argue in favor of breaking down large genera. For instance,

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2688-474: Is the type species , and the generic name is permanently associated with the type specimen of its type species. Should the specimen turn out to be assignable to another genus, the generic name linked to it becomes a junior synonym and the remaining taxa in the former genus need to be reassessed. In zoological usage, taxonomic names, including those of genera, are classified as "available" or "unavailable". Available names are those published in accordance with

2772-640: Is the Coast Redwood Sequoia sempervirens , which is a hexaploid (6 x ) with 66 chromosomes (2 n = 6 x = 66), although the origin is unclear. Aquatic plants, especially the Monocotyledons , include a large number of polyploids. The induction of polyploidy is a common technique to overcome the sterility of a hybrid species during plant breeding. For example, triticale is the hybrid of wheat ( Triticum turgidum ) and rye ( Secale cereale ). It combines sought-after characteristics of

2856-555: Is under- or over-represented are said to be aneuploid (from the Greek words meaning "not", "good", and "fold"). Aneuploidy refers to a numerical change in part of the chromosome set, whereas polyploidy refers to a numerical change in the whole set of chromosomes. Polyploidy occurs in some tissues of animals that are otherwise diploid, such as human muscle tissues. This is known as endopolyploidy . Species whose cells do not have nuclei, that is, prokaryotes , may be polyploid, as seen in

2940-621: The International Code of Zoological Nomenclature ; the earliest such name for any taxon (for example, a genus) should then be selected as the " valid " (i.e., current or accepted) name for the taxon in question. Consequently, there will be more available names than valid names at any point in time; which names are currently in use depending on the judgement of taxonomists in either combining taxa described under multiple names, or splitting taxa which may bring available names previously treated as synonyms back into use. "Unavailable" names in zoology comprise names that either were not published according to

3024-824: The International Plant Names Index for plants in general, and ferns through angiosperms, respectively, and Nomenclator Zoologicus and the Index to Organism Names for zoological names. Totals for both "all names" and estimates for "accepted names" as held in the Interim Register of Marine and Nonmarine Genera (IRMNG) are broken down further in the publication by Rees et al., 2020 cited above. The accepted names estimates are as follows, broken down by kingdom: The cited ranges of uncertainty arise because IRMNG lists "uncertain" names (not researched therein) in addition to known "accepted" names;

3108-546: The basidiomycota Microbotryum violaceum ). As for plants and animals, fungal hybrids and polyploids display structural and functional modifications compared to their progenitors and diploid counterparts. In particular, the structural and functional outcomes of polyploid Saccharomyces genomes strikingly reflect the evolutionary fate of plant polyploid ones. Large chromosomal rearrangements leading to chimeric chromosomes have been described, as well as more punctual genetic modifications such as gene loss. The homoealleles of

3192-419: The nomenclature codes , which allow each species a single unique name that, for animals (including protists ), plants (also including algae and fungi ) and prokaryotes ( bacteria and archaea ), is Latin and binomial in form; this contrasts with common or vernacular names , which are non-standardized, can be non-unique, and typically also vary by country and language of usage. Except for viruses ,

3276-404: The platypus belongs to the genus Ornithorhynchus although George Shaw named it Platypus in 1799 (these two names are thus synonyms ) . However, the name Platypus had already been given to a group of ambrosia beetles by Johann Friedrich Wilhelm Herbst in 1793. A name that means two different things is a homonym . Since beetles and platypuses are both members of the kingdom Animalia,

3360-664: The salmonids and many cyprinids (i.e. carp ). Some fish have as many as 400 chromosomes. Polyploidy also occurs commonly in amphibians; for example the biomedically important genus Xenopus contains many different species with as many as 12 sets of chromosomes (dodecaploid). Polyploid lizards are also quite common. Most are sterile and reproduce by parthenogenesis ; others, like Liolaemus chiliensis , maintain sexual reproduction. Polyploid mole salamanders (mostly triploids) are all female and reproduce by kleptogenesis , "stealing" spermatophores from diploid males of related species to trigger egg development but not incorporating

3444-420: The vertebrates (which includes the human lineage) and another near the origin of the teleost fishes . Angiosperms ( flowering plants ) have paleopolyploidy in their ancestry. All eukaryotes probably have experienced a polyploidy event at some point in their evolutionary history. A karyotype is the characteristic chromosome complement of a eukaryote species . The preparation and study of karyotypes

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3528-508: The Cyprininae –, as they seem to be as distinct from barbels and typical carps , as these are from the garras (which are part of the disputed Labeoninae), rendering the old "Barbinae" paraphyletic . Within the small African barbs, several lineages can be recognized. These are mostly diploid ; a tetraploid group largely restricted to southern Africa is very close to Pseudobarbus and might even be included therein. In particular,

3612-425: The agamic complexes of Crepis . Some plants are triploid. As meiosis is disturbed, these plants are sterile, with all plants having the same genetic constitution: Among them, the exclusively vegetatively propagated saffron crocus ( Crocus sativus ). Also, the extremely rare Tasmanian shrub Lomatia tasmanica is a triploid sterile species. There are few naturally occurring polyploid conifers . One example

3696-575: The allotetraploid yeast S. pastorianus show unequal contribution to the transcriptome . Phenotypic diversification is also observed following polyploidization and/or hybridization in fungi, producing the fuel for natural selection and subsequent adaptation and speciation. Other eukaryotic taxa have experienced one or more polyploidization events during their evolutionary history (see Albertin and Marullo, 2012 for review). The oomycetes , which are non-true fungi members, contain several examples of paleopolyploid and polyploid species, such as within

3780-442: The base for higher taxonomic ranks, such as the family name Canidae ("Canids") based on Canis . However, this does not typically ascend more than one or two levels: the order to which dogs and wolves belong is Carnivora ("Carnivores"). The numbers of either accepted, or all published genus names is not known precisely; Rees et al., 2020 estimate that approximately 310,000 accepted names (valid taxa) may exist, out of

3864-567: The basis for a range of studies in what might be called evolutionary cytology. Homoeologous chromosomes are those brought together following inter-species hybridization and allopolyploidization , and whose relationship was completely homologous in an ancestral species. For example, durum wheat is the result of the inter-species hybridization of two diploid grass species Triticum urartu and Aegilops speltoides . Both diploid ancestors had two sets of 7 chromosomes, which were similar in terms of size and genes contained on them. Durum wheat contains

3948-432: The best known is colchicine , which can result in chromosome doubling, though its use may have other less obvious consequences as well. Oryzalin will also double the existing chromosome content. Among mammals , a high frequency of polyploid cells is found in organs such as the brain, liver, heart, and bone marrow. It also occurs in the somatic cells of other animals , such as goldfish , salmon , and salamanders . It

4032-536: The closest living relatives – of Aulopyge huegelii . Carasobarbus and Labeobarbus are probably closely related to this group, too, and some large hexaploid barbs (e.g. L. reinii ) may well belong in Labeobarbus . The small barbs from Africa, by contrast, are quite distinct. They might even warrant establishment of a new subfamily – in particular if the Labeoninae are not included in

4116-457: The common name of bread wheat. Many agriculturally important plants of the genus Brassica are also tetraploids. Sugarcane can have ploidy levels higher than octaploid . Polyploidization can be a mechanism of  sympatric speciation  because polyploids are usually unable to interbreed with their diploid ancestors. An example is the plant Erythranthe peregrina . Sequencing confirmed that this species originated from E. × robertsii ,

4200-407: The diploid species. A similar relationship exists between three diploid species of Tragopogon ( T. dubius , T. pratensis , and T. porrifolius ) and two allotetraploid species ( T. mirus and T. miscellus ). Complex patterns of allopolyploid evolution have also been observed in animals, as in the frog genus Xenopus . Organisms in which a particular chromosome, or chromosome segment,

4284-581: The ends of a spectrum of divergence between parental subgenomes. Polyploids that fall between these two extremes, which are often referred to as segmental allopolyploids, may display intermediate levels of polysomic inheritance that vary by locus. About half of all polyploids are thought to be the result of autopolyploidy, although many factors make this proportion hard to estimate. Allopolyploids or amphipolyploids or heteropolyploids are polyploids with chromosomes derived from two or more diverged taxa. As in autopolyploidy, this primarily occurs through

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4368-471: The evolved polyploids. The high degree of homology among duplicated chromosomes causes autopolyploids to display polysomic inheritance . This trait is often used as a diagnostic criterion to distinguish autopolyploids from allopolyploids, which commonly display disomic inheritance after they progress past the neopolyploid stage. While most polyploid species are unambiguously characterized as either autopolyploid or allopolyploid, these categories represent

4452-455: The fact that most members of the genera have a pair of barbels on their mouths, which they can use to search for food at the bottom of the water. Barbels are often fished for food; in some locations they are of commercial significance. The roe of barbels is poisonous, however. The large Barbus barbs are also often eaten in their native range. The smaller barbs are in some cases traded as aquarium fish. Some are quite significant, but as

4536-446: The form "author, year" in zoology, and "standard abbreviated author name" in botany. Thus in the examples above, the genus Canis would be cited in full as " Canis Linnaeus, 1758" (zoological usage), while Hibiscus , also first established by Linnaeus but in 1753, is simply " Hibiscus L." (botanical usage). Each genus should have a designated type , although in practice there is a backlog of older names without one. In zoology, this

4620-613: The four expected if it were truly a tetraploid. This rodent is not a rat , but kin to guinea pigs and chinchillas . Its "new" diploid (2 n ) number is 102 and so its cells are roughly twice normal size. Its closest living relation is Octomys mimax , the Andean Viscacha-Rat of the same family, whose 2 n = 56. It was therefore surmised that an Octomys -like ancestor produced tetraploid (i.e., 2 n = 4 x = 112) offspring that were, by virtue of their doubled chromosomes, reproductively isolated from their parents. Polyploidy

4704-436: The frog, Xenopus (an extension of the work of Briggs and King in 1952) that were able to develop to the tadpole stage. The British scientist J. B. S. Haldane hailed the work for its potential medical applications and, in describing the results, became one of the first to use the word " clone " in reference to animals. Later work by Shinya Yamanaka showed how mature cells can be reprogrammed to become pluripotent, extending

4788-425: The fusion of unreduced (2 n ) gametes, which can take place before or after hybridization . In the former case, unreduced gametes from each diploid taxon – or reduced gametes from two autotetraploid taxa – combine to form allopolyploid offspring. In the latter case, one or more diploid F 1 hybrids produce unreduced gametes that fuse to form allopolyploid progeny. Hybridization followed by genome duplication may be

4872-509: The fusion of unreduced (2 n ) gametes, which results in either triploid ( n + 2 n = 3 n ) or tetraploid (2 n + 2 n = 4 n ) offspring. Triploid offspring are typically sterile (as in the phenomenon of triploid block ), but in some cases they may produce high proportions of unreduced gametes and thus aid the formation of tetraploids. This pathway to tetraploidy is referred to as the triploid bridge . Triploids may also persist through asexual reproduction . In fact, stable autotriploidy in plants

4956-737: The generic name (or its abbreviated form) still forms the leading portion of the scientific name, for example, Canis lupus lupus for the Eurasian wolf subspecies, or as a botanical example, Hibiscus arnottianus ssp. immaculatus . Also, as visible in the above examples, the Latinised portions of the scientific names of genera and their included species (and infraspecies, where applicable) are, by convention, written in italics . The scientific names of virus species are descriptive, not binomial in form, and may or may not incorporate an indication of their containing genus; for example,

5040-653: The genus Phytophthora . Some species of brown algae ( Fucales , Laminariales and diatoms ) contain apparent polyploid genomes. In the Alveolata group, the remarkable species Paramecium tetraurelia underwent three successive rounds of whole-genome duplication and established itself as a major model for paleopolyploid studies. Each Deinococcus radiodurans bacterium contains 4-8 copies of its chromosome . Exposure of D. radiodurans to X-ray irradiation or desiccation can shatter its genomes into hundred of short random fragments. Nevertheless, D. radiodurans

5124-558: The group called "redfins" may well be monophyletic and belong in Pseudobarbus entirely, instead of being split between Pseudobarbus and Barbus . There are currently 36 recognized species of this genus: A fossil species ( Barbus megacephalus Günther, 1876 ) is known from the Paleogene Sipang Fauna of Indonesia ., but it probably should be placed in another genus. Genus The composition of

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5208-429: The large bacterium Epulopiscium fishelsoni . Hence ploidy is defined with respect to a cell. A monoploid has only one set of chromosomes and the term is usually only applied to cells or organisms that are normally diploid. The more general term for such organisms is haploid . A polyploid that is newly formed. That has become polyploid in more recent history; it is not as new as a neopolyploid and not as old as

5292-633: The largest component, with 23,236 ± 5,379 accepted genus names, of which 20,845 ± 4,494 are angiosperms (superclass Angiospermae). By comparison, the 2018 annual edition of the Catalogue of Life (estimated >90% complete, for extant species in the main) contains currently 175,363 "accepted" genus names for 1,744,204 living and 59,284 extinct species, also including genus names only (no species) for some groups. The number of species in genera varies considerably among taxonomic groups. For instance, among (non-avian) reptiles , which have about 1180 genera,

5376-488: The lizard genus Anolis has been suggested to be broken down into 8 or so different genera which would bring its ~400 species to smaller, more manageable subsets. Tetraploid Polyploidy is a condition in which the cells of an organism have more than two paired sets of ( homologous ) chromosomes . Most species whose cells have nuclei ( eukaryotes ) are diploid , meaning they have two complete sets of chromosomes, one from each of two parents; each set contains

5460-518: The males' DNA into the offspring. While some tissues of mammals, such as parenchymal liver cells, are polyploid, rare instances of polyploid mammals are known, but most often result in prenatal death. An octodontid rodent of Argentina 's harsh desert regions, known as the plains viscacha rat ( Tympanoctomys barrerae ) has been reported as an exception to this 'rule'. However, careful analysis using chromosome paints shows that there are only two copies of each chromosome in T. barrerae , not

5544-403: The most (>300) have only 1 species, ~360 have between 2 and 4 species, 260 have 5–10 species, ~200 have 11–50 species, and only 27 genera have more than 50 species. However, some insect genera such as the bee genera Lasioglossum and Andrena have over 1000 species each. The largest flowering plant genus, Astragalus , contains over 3,000 species. Which species are assigned to a genus

5628-428: The name could not be used for both. Johann Friedrich Blumenbach published the replacement name Ornithorhynchus in 1800. However, a genus in one kingdom is allowed to bear a scientific name that is in use as a generic name (or the name of a taxon in another rank) in a kingdom that is governed by a different nomenclature code. Names with the same form but applying to different taxa are called "homonyms". Although this

5712-408: The number of chromosome sets in the nucleus . The letter x is used to represent the number of chromosomes in a single set: Autopolyploids are polyploids with multiple chromosome sets derived from a single taxon . Two examples of natural autopolyploids are the piggyback plant, Tolmiea menzisii and the white sturgeon, Acipenser transmontanum . Most instances of autopolyploidy result from

5796-417: The parents, but the initial hybrids are sterile. After polyploidization, the hybrid becomes fertile and can thus be further propagated to become triticale. In some situations, polyploid crops are preferred because they are sterile. For example, many seedless fruit varieties are seedless as a result of polyploidy. Such crops are propagated using asexual techniques, such as grafting . Polyploidy in crop plants

5880-721: The possibilities to non-stem cells. Gurdon and Yamanaka were jointly awarded the Nobel Prize in 2012 for this work. True polyploidy rarely occurs in humans, although polyploid cells occur in highly differentiated tissue, such as liver parenchyma , heart muscle, placenta and in bone marrow. Aneuploidy is more common. Polyploidy occurs in humans in the form of triploidy , with 69 chromosomes (sometimes called 69, XXX), and tetraploidy with 92 chromosomes (sometimes called 92, XXXX). Triploidy, usually due to polyspermy , occurs in about 2–3% of all human pregnancies and ~15% of miscarriages. The vast majority of triploid conceptions end as

5964-550: The prevalence of allopolyploidy among crop species. Both bread wheat and triticale are examples of an allopolyploids with six chromosome sets. Cotton , peanut , and quinoa are allotetraploids with multiple origins. In Brassicaceous crops, the Triangle of U describes the relationships between the three common diploid Brassicas ( B. oleracea , B. rapa , and B. nigra ) and three allotetraploids ( B. napus , B. juncea , and B. carinata ) derived from hybridization among

6048-796: The processes of speciation and eco-niche exploitation. The mechanisms leading to novel variation in newly formed allopolyploids may include gene dosage effects (resulting from more numerous copies of genome content), the reunion of divergent gene regulatory hierarchies, chromosomal rearrangements, and epigenetic remodeling, all of which affect gene content and/or expression levels. Many of these rapid changes may contribute to reproductive isolation and speciation. However, seed generated from interploidy crosses , such as between polyploids and their parent species, usually have aberrant endosperm development which impairs their viability, thus contributing to polyploid speciation . Polyploids may also interbreed with diploids and produce polyploid seeds, as observed in

6132-460: The production of aneuploid gametes. Natural or artificial selection for fertility can quickly stabilize meiosis in autopolyploids by restoring bivalent pairing during meiosis. Rapid adaptive evolution of the meiotic machinery, resulting in reduced levels of multivalents (and therefore stable autopolyploid meiosis) has been documented in Arabidopsis arenosa and Arabidopsis lyrata , with specific adaptive alleles of these species shared between only

6216-419: The production of polyploid cells. This process can be useful in plant breeding, especially when attempting to introgress germplasm across ploidal levels. Autopolyploids possess at least three homologous chromosome sets, which can lead to high rates of multivalent pairing during meiosis (particularly in recently formed autopolyploids, also known as neopolyploids) and an associated decrease in fertility due to

6300-541: The provisions of the ICZN Code, e.g., incorrect original or subsequent spellings, names published only in a thesis, and generic names published after 1930 with no type species indicated. According to "Glossary" section of the zoological Code, suppressed names (per published "Opinions" of the International Commission of Zoological Nomenclature) remain available but cannot be used as the valid name for

6384-470: The same kind as other (analogous) genera. The term "genus" comes from Latin genus , a noun form cognate with gignere ('to bear; to give birth to'). The Swedish taxonomist Carl Linnaeus popularized its use in his 1753 Species Plantarum , but the French botanist Joseph Pitton de Tournefort (1656–1708) is considered "the founder of the modern concept of genera". The scientific name (or

6468-642: The same number of chromosomes, and the chromosomes are joined in pairs of homologous chromosomes. However, some organisms are polyploid . Polyploidy is especially common in plants. Most eukaryotes have diploid somatic cells , but produce haploid gametes (eggs and sperm) by meiosis . A monoploid has only one set of chromosomes, and the term is usually only applied to cells or organisms that are normally diploid. Males of bees and other Hymenoptera , for example, are monoploid. Unlike animals, plants and multicellular algae have life cycles with two alternating multicellular generations . The gametophyte generation

6552-408: The scientific epithet) of a genus is also called the generic name ; in modern style guides and science, it is always capitalised. It plays a fundamental role in binomial nomenclature , the system of naming organisms , where it is combined with the scientific name of a species : see Botanical name and Specific name (zoology) . The rules for the scientific names of organisms are laid down in

6636-497: The specific name particular to the wolf. A botanical example would be Hibiscus arnottianus , a particular species of the genus Hibiscus native to Hawaii. The specific name is written in lower-case and may be followed by subspecies names in zoology or a variety of infraspecific names in botany . When the generic name is already known from context, it may be shortened to its initial letter, for example, C. lupus in place of Canis lupus . Where species are further subdivided,

6720-412: The standard format for a species name comprises the generic name, indicating the genus to which the species belongs, followed by the specific epithet, which (within that genus) is unique to the species. For example, the gray wolf 's scientific name is Canis lupus , with Canis ( Latin for 'dog') being the generic name shared by the wolf's close relatives and lupus (Latin for 'wolf') being

6804-403: The taxon is termed a synonym ; some authors also include unavailable names in lists of synonyms as well as available names, such as misspellings, names previously published without fulfilling all of the requirements of the relevant nomenclatural code, and rejected or suppressed names. A particular genus name may have zero to many synonyms, the latter case generally if the genus has been known for

6888-576: The values quoted are the mean of "accepted" names alone (all "uncertain" names treated as unaccepted) and "accepted + uncertain" names (all "uncertain" names treated as accepted), with the associated range of uncertainty indicating these two extremes. Within Animalia, the largest phylum is Arthropoda , with 151,697 ± 33,160 accepted genus names, of which 114,387 ± 27,654 are insects (class Insecta). Within Plantae, Tracheophyta (vascular plants) make up

6972-429: The virus species " Salmonid herpesvirus 1 ", " Salmonid herpesvirus 2 " and " Salmonid herpesvirus 3 " are all within the genus Salmonivirus ; however, the genus to which the species with the formal names " Everglades virus " and " Ross River virus " are assigned is Alphavirus . As with scientific names at other ranks, in all groups other than viruses, names of genera may be cited with their authorities, typically in

7056-412: Was induced in fish by Har Swarup (1956) using a cold-shock treatment of the eggs close to the time of fertilization, which produced triploid embryos that successfully matured. Cold or heat shock has also been shown to result in unreduced amphibian gametes, though this occurs more commonly in eggs than in sperm. John Gurdon (1958) transplanted intact nuclei from somatic cells to produce diploid eggs in

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