Polyploidy

tetraploidpolyploidtriploidhexaploidallotetraploidallopolyploidoctoploidtetraploidyamphidiploidpentaploid
Polyploidy is the state of a cell or organism having more than two paired (homologous) sets of chromosomes.wikipedia
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Durum

durum wheathard wheatT. durum
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 the common name of bread wheat.
durum), is a tetraploid species of wheat.

Erythranthe peregrina

E. peregrinaMimulus peregrinus
An example is the plant Erythranthe peregrina.
This species is a rare example of polyploidization and speciation where sterility did not occur.

Dahlia

dahliasDahlia the TricksterDahlia variabilis
octaploid or octoploid, (eight sets; 8x), for example Acipenser (genus of sturgeon fish), dahlias
This great variety results from dahlias being octoploids—that is, they have eight sets of homologous chromosomes, whereas most plants have only two.

Xenopus

African Clawed Frog (Toad)clawed frogfrog
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).
The genus is also known for its polyploidy, with some species having up to 12 sets of chromosomes.

Species

specificspecific namespecific epithet
It occurs in the somatic cells of some animals, such as goldfish, salmon, and salamanders, but is especially common among ferns and flowering plants (see Hibiscus rosa-sinensis), including both wild and cultivated species.
Genes can sometimes be exchanged between species by horizontal gene transfer; new species can arise rapidly through hybridisation and polyploidy; and species may become extinct for a variety of reasons.

Epulopiscium fishelsoni

This is known as endopolyploidy. Species whose cells do not have nuclei, that is, prokaryotes, may be polyploid, as seen in the large bacterium Epulopiscium fishelsoni.
are extremely polyploid, with bacterial chromosomes representing hundreds of thousands of copies of the genome.

Spartina anglica

common cord grassCommon cord-grassCommon Cordgrass
dodecaploid (twelve sets; 12x), for example the plants Celosia argentea and Spartina anglica or the amphibian Xenopus ruwenzoriensis.
It is an allotetraploid species derived from the hybrid Spartina × townsendii, which arose when the European native cordgrass Spartina maritima (Small Cordgrass) hybridised with the introduced American Spartina alterniflora (Smooth Cordgrass).

Wheat

cornTriticumdwarf wheat
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 the common name of bread wheat.
Some wheat species are diploid, with two sets of chromosomes, but many are stable polyploids, with four sets of chromosomes (tetraploid) or six (hexaploid).

Fragaria

wild strawberrystrawberriesstrawberry
decaploid (ten sets; 10x), for example certain strawberries
However, they exhibit different polyploidy.

Sympatric speciation

sympatricsympatrysympatrically
Polyploidization is a mechanism of sympatric speciation because polyploids are usually unable to interbreed with their diploid ancestors.
Sympatric speciation events are quite common in plants, which are prone to acquiring multiple homologous sets of chromosomes, resulting in polyploidy.

Chromosome

chromosomeschromosomalChromosomal number
Polyploidy is the state of a cell or organism having more than two paired (homologous) sets of chromosomes.
Some animal and plant species are polyploid [Xn]: They have more than two sets of homologous chromosomes.

Fertilisation

fertilizationconceptionfertilized
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.
During double fertilisation in angiosperms the haploid male gamete combines with two haploid polar nuclei to form a triploid primary endosperm nucleus by the process of vegetative fertilisation.

Har Swarup

Polyploidy 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.
He is known for his research at Oxford University on polyploidy, cloning, nuclear transfer and later for his many other researches such as the discovery of "ringed polysome figures" and on theories on gene expression changes with evolution and environment.

Sturgeon

sturgeonsAcipenseridaeGulf sturgeon
octaploid or octoploid, (eight sets; 8x), for example Acipenser (genus of sturgeon fish), dahlias
Sturgeons are polyploid; some species have four, eight, or 16 sets of chromosomes.

Hibiscus rosa-sinensis

Chinese hibiscusH. rosa-sinensisbunga raya
It occurs in the somatic cells of some animals, such as goldfish, salmon, and salamanders, but is especially common among ferns and flowering plants (see Hibiscus rosa-sinensis), including both wild and cultivated species.
Hibiscus rosa-sinensis is one of many plant species with a genetic characteristic known as polyploidy, in which there are more than two complete sets of chromosomes, unlike most other species.

Paleopolyploidy

whole genome duplicationWhole-genome duplicationancient genome duplications (paleopolyploidy)
Polyploidy is pervasive in plants and some estimates suggest that 30–80% of living plant species are polyploid, and many lineages show evidence of ancient polyploidy (paleopolyploidy) in their genomes.
Paleopolyploidy is the result of genome duplications which occurred at least several million years ago (MYA).

Ploidy

diploidhaploid2n
Most species whose cells have nuclei (eukaryotes) are diploid, meaning they have two sets of chromosomes—one set inherited from each parent.
Somatic cells, tissues and individuals can be described according to the number of sets present (the ploidy level): monoploid (1 set), diploid (2 sets), triploid (3 sets), tetraploid (4 sets), pentaploid (5 sets), hexaploid (6 sets), heptaploid or septaploid (7 sets), etc. The generic term polyploid is used to describe cells with three or more chromosome sets.

Somatic cell

somatic cellssomaticvegetative cell
Most eukaryotes have diploid somatic cells, but produce haploid gametes (eggs and sperm) by meiosis.
However, a large number of species have the chromosomes in their somatic cells arranged in fours ("tetraploid") or even sixes ("hexaploid").

Mountain viscacha rat

mountain vizcacha ratO. mimaxviscacha rat
Its closest living relation is Octomys mimax, the Andean Viscacha-Rat of the same family, whose 2n = 56. It was therefore surmised that an Octomys-like ancestor produced tetraploid (i.e., 2n = 4x = 112) offspring that were, by virtue of their doubled chromosomes, reproductively isolated from their parents.
It is the only living species within the genus Octomys. This diploid genus (2n = 56) may be ancestral to the two unusual suspected tetraploid species Tympanoctomys barrerae and Pipanacoctomys aureus.

Octodontidae

octodontidOctodontidae indet.octodontids
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'.
There is some evidence that evolution within the family may have resulted from polyploidy.

Lomatia tasmanica

King's LomatiaL. tasmanica
Lomatia tasmanica is an extremely rare Tasmanian shrub that is triploid and sterile; reproduction is entirely vegetative, with all plants having the same genetic constitution.
Because it has three sets of chromosomes (a triploid) and is therefore sterile, reproduction occurs only vegetatively: when a branch falls, that branch grows new roots, establishing a new plant that is genetically identical to its parent.

Molar pregnancy

hydatidiform molemolar pregnancieshydatid mole
In diandry, a partial hydatidiform mole develops.
In contrast, a partial mole occurs when a normal egg is fertilized by one or two sperm which then reduplicates itself, yielding the genotypes of 69,XXY (triploid) or 92,XXXY (tetraploid).

Ribston Pippin

Essex Pippin
Triploid crops: some apple varieties (e.g. Belle de Boskoop, Jonagold, Mutsu, Ribston Pippin), banana, citrus, ginger, watermelon
'Ribston Pippin' is a triploid cultivar of apples, also known by other names including 'Essex Pippin', 'Beautiful Pippin', 'Formosa', 'Glory of York', 'Ribstone', 'Rockhill's Russet', 'Travers', and 'Travers's Reinette'.

Speciation

divergedspeciatedtrichotomy
It has been established that 15% of angiosperm and 31% of fern speciation events are accompanied by ploidy increase.
Rapid sympatric speciation can take place through polyploidy, such as by doubling of chromosome number; the result is progeny which are immediately reproductively isolated from the parent population.

Miscarriage

miscarriedspontaneous abortionmiscarriages
The vast majority of triploid conceptions end as a miscarriage; those that do survive to term typically die shortly after birth.
Common chromosome abnormalities found in miscarriages include autosomal trisomy (22-32%), monosomy X (5-20%), triploidy (6-8%), tetraploidy (2-4%), or other structural chromosomal abnormalities (2%).