Editing Ploidy (section)

=== Polyploidy ===
{{main |Polyploidy}}
'''Polyploidy''' is the state where all cells have multiple sets of chromosomes beyond the basic set, usually 3 or more. Specific terms are '''triploid''' (3 sets), '''tetraploid''' (4 sets), pentaploid (5 sets), hexaploid (6 sets), heptaploid<ref name="Murty-1973"/> or septaploid<ref name="Tateoka-1975"/> (7 sets), octoploid (8 sets), nonaploid (9 sets), decaploid (10 sets), undecaploid (11 sets), dodecaploid (12 sets), tridecaploid (13 sets), tetradecaploid (14 sets), etc.<ref name="Dierschke-2009">{{cite journal |vauthors=Dierschke T, Mandáková T, Lysak MA, Mummenhoff K | title=A bicontinental origin of polyploid Australian/New Zealand ''Lepidium'' species (Brassicaceae)? Evidence from genomic in situ hybridization | journal=Annals of Botany | volume=104 | issue=4 | pages=681–688 | date=September 2009 | pmid=19589857 | pmc=2729636 | doi=10.1093/aob/mcp161 }}</ref><ref name="Renny-Byfield-2010">{{cite journal |url= |title=Flow cytometry and GISH reveal mixed ploidy populations and Spartina nonaploids with genomes of ''S. alterniflora'' and ''S. maritima'' origin |author=Simon Renny-Byfield |journal=Annals of Botany |year=2010 |volume=105 |issue=4 |pages=527–533 |doi=10.1093/aob/mcq008 |display-authors=etal |pmid=20150197 |pmc=2850792}}</ref><ref name="Hummer-2009">{{cite journal |title=Decaploidy in ''Fragaria iturupensis'' (Rosaceae) |author=Kim E. Hummer |journal=Am. J. Bot. |date=March 2009 |volume=96 |number=3 |pages=713–716 |doi=10.3732/ajb.0800285 |pmid=21628226 |display-authors=etal|doi-access=free }}</ref><ref name="Talyshinskiĭ-1990">{{cite journal |url=http://www.cabdirect.org/abstracts/19911699005.html |title=Study of the fractional composition of the proteins in the compound fruit of polyploid mulberry |author=Talyshinskiĭ, G. M. |journal=Shelk |year=1990 |number=5 |pages=8–10}}</ref> Some higher ploidies include hexadecaploid (16 sets), dotriacontaploid (32 sets), and tetrahexacontaploid (64 sets),<ref>{{cite journal |url=https://www.jstage.jst.go.jp/article/csf/26/5/26_5_263/_pdf |title=Temperature dependence in Proliferation of tetraploid Meth-A cells in comparison with the parent diploid cells |author=Fujikawa-Yamamoto K |journal=Cell Structure and Function |volume=26 |issue=5 |pages=263–269 |year=2001 |doi=10.1247/csf.26.263|pmid=11831358 |doi-access=free }}</ref> though Greek terminology may be set aside for readability in cases of higher ploidy (such as "16-ploid").<ref name="Hummer-2009" /> [[Polytene chromosomes]] of plants and fruit flies can be 1024-ploid.<ref>{{cite book |url=https://books.google.com/books?id=Nrjn1kzN0_0C&pg=PA68 |title=Plant Chromosomes: Laboratory Methods |author1=Kiichi Fukui |author2=Shigeki Nakayama |isbn=9780849389191 |date=1996 |publisher=CRC Press }}</ref><ref>{{cite web |url=http://cricket.bio.indiana.edu/allied-data/lk/interactive-fly/aimorph/puffing.htm |title=Genes involved in tissue and organ development: Polytene chromosomes, endoreduplication and puffing |publisher=The Interactive Fly |access-date=2012-12-16 |archive-url=https://web.archive.org/web/20050504235437/http://cricket.bio.indiana.edu/allied-data/lk/interactive-fly/aimorph/puffing.htm |archive-date=2005-05-04 |url-status=dead }}</ref> Ploidy of systems such as the [[salivary gland]], [[elaiosome]], [[endosperm]], and [[trophoblast]] can exceed this, up to 1048576-ploid in the silk glands of the commercial silkworm ''[[Bombyx mori]]''.<ref name="D'Amato-2002" />

The chromosome sets may be from the same species or from closely related species. In the latter case, these are known as allopolyploids (or amphidiploids, which are allopolyploids that behave as if they were normal diploids). Allopolyploids are formed from the hybridization of two separate species. In plants, this probably most often occurs from the pairing of meiotically unreduced [[gametes]], and not by diploid–diploid hybridization followed by chromosome doubling.<ref>{{cite journal |last1=Ramsey |first1=Justin |last2=Schemske |first2=Douglas W. |title=Neopolyploidy in Flowering Plants |journal=Annual Review of Ecology and Systematics |date=November 2002 |volume=33 |issue=1 |pages=589–639 |doi=10.1146/annurev.ecolsys.33.010802.150437 |bibcode=2002AnRES..33..589R }}</ref> The so-called [[Triangle of U|''Brassica'' triangle]] is an example of allopolyploidy, where three different parent species have hybridized in all possible pair combinations to produce three new species.<ref>{{Cite journal |last1=Song |first1=Xiaoming |last2=Wei |first2=Yanping |last3=Xiao |first3=Dong |last4=Gong |first4=Ke |last5=Sun |first5=Pengchuan |last6=Ren |first6=Yiming |last7=Yuan |first7=Jiaqing |last8=Wu |first8=Tong |last9=Yang |first9=Qihang |last10=Li |first10=Xinyu |last11=Nie |first11=Fulei |last12=Li |first12=Nan |last13=Feng |first13=Shuyan |last14=Pei |first14=Qiaoying |last15=Yu |first15=Tong |date=2021-02-04 |title=Brassica carinata genome characterization clarifies U's triangle model of evolution and polyploidy in Brassica |journal=Plant Physiology |volume=186 |issue=1 |pages=388–406 |doi=10.1093/plphys/kiab048 |issn=0032-0889 |pmc=8154070 |pmid=33599732}}</ref>

Polyploidy occurs commonly in plants, but rarely in animals. Even in diploid organisms, many [[somatic cell]]s are polyploid due to a process called [[endoreduplication]], where duplication of the [[genome]] occurs without [[mitosis]] (cell division). The extreme in polyploidy occurs in the [[fern]] genus ''[[Ophioglossum]]'', the adder's-tongues, in which polyploidy results in chromosome counts in the hundreds, or, in at least one case, well over one thousand.{{citation needed|date=May 2023}}

It is possible for polyploid organisms to revert to lower ploidy by [[haploidisation]].{{citation needed|date=May 2023}}

====In bacteria and archaea====
[[Polyploid]]y is a characteristic of the bacterium ''[[Deinococcus radiodurans]]'' <ref name="Hansen-1978">{{cite journal |vauthors=Hansen MT |title=Multiplicity of genome equivalents in the radiation-resistant bacterium Micrococcus radiodurans |journal=J. Bacteriol. |volume=134 |issue=1 |pages=71–75 |year=1978 |pmid=649572 |pmc=222219 |doi= 10.1128/JB.134.1.71-75.1978}}</ref> and of the [[archaea|archaeon]] ''[[Halobacterium salinarum]]''.<ref name="Soppa-2011">{{cite journal |vauthors=Soppa J |title=Ploidy and gene conversion in Archaea |journal=Biochem. Soc. Trans. |volume=39 |issue=1 |pages=150–154 |year=2011 |pmid=21265763 |doi=10.1042/BST0390150 |s2cid=31385928 }}</ref> These two species are highly resistant to [[ionizing radiation]] and [[desiccation]], conditions that induce [[DNA]] double-strand breaks.<ref name="Zahradka-2006">{{cite journal |vauthors=Zahradka K, Slade D, Bailone A, Sommer S, Averbeck D, Petranovic M, Lindner AB, Radman M |title=Reassembly of shattered chromosomes in Deinococcus radiodurans |journal=Nature |volume=443 |issue=7111 |pages=569–573 |year=2006 |pmid=17006450 |doi=10.1038/nature05160 |bibcode=2006Natur.443..569Z |s2cid=4412830 }}</ref><ref name="Kottemann-2005">{{cite journal |vauthors=Kottemann M, Kish A, Iloanusi C, Bjork S, DiRuggiero J |title=Physiological responses of the halophilic archaeon Halobacterium sp. strain NRC1 to desiccation and gamma irradiation |journal=Extremophiles |volume=9 |issue=3 |pages=219–227 |year=2005 |pmid=15844015 |doi=10.1007/s00792-005-0437-4 |s2cid=8391234 |url=https://hal-mnhn.archives-ouvertes.fr/mnhn-02862359/file/2005_Kottemann_Kish_NRC1%20physiological%20response%20to%20desiccation%20and%20gamma%20radiation.pdf }}</ref> This resistance appears to be due to efficient [[homologous recombination]]al repair.