Ploidy
(Redirected from Haploids)
Ploidy is a term from genetics and cell biology. It is used to indicate the number of chromosome sets in a cell. Most eukaryotes have either one set (called haploid) or two sets (called diploid). Some other organisms are polyploid, they have more than two sets of chromosomes. Some amphibians are triploid, with 3 sets. The endosperm cells in the seeds of many plants are also triploid. Some kinds of trout or salmon have 4 sets (tetraploid). Other examples:
- wheat: 6 sets (hectaploid)
- certain sturgeons: 8 sets (octoploid)
- strawberries: 8 sets (octoploid)
- plumed cockscomb (a plant, Celosia argentea): 12 sets (dodecaploid)
- Bryophytes: body has one set; sporophyte has two sets.
Sex cells (gametes) are almost always haploid. If the reproductive stage (adult) is polyploid, then the gametes will have half the ploidy number of chromosomes.
There are some variations of ploidy which are not discussed here. Some plant species with certain types of polyploidy do not use sexual reproduction, but survive with asexual methods.
Polyploidy[edit | edit source]
Polyploidy occurs in cells and organisms when there are more than two paired (homologous) sets of chromosomes.
Most organisms are normally diploid, meaning they have two sets of chromosomes — one set inherited from each parent. Polyploidy may occur due to abnormal cell division. It is most commonly found in plants, but it does sometimes happen in animals.[1] Some estimates suggest that 30-80% of living plant species are polyploid, and many lineages show evidence of ancient polyploidy (paleopolyploidy) in their genomes.[2] Huge increases in angiosperm (flowering plants) diversity have coincided with the timing of ancient genome duplications shared by many species.[3] 15% of angiosperm and 31% of fern speciation events are accompanied by ploidy increase.[4][5]
Polyploid plants arise spontaneously in nature. Many polyploids are fitter than their parental species, and may display novel variation or morphologies that contribute to speciation and eco-niche exploitation.[6][7][8]
Polyploidy may occur in one generation, and is an exception to the principle that evolution occurs gradually. There may, however, be many genetic changes in the species after polyploidy has taken place.
Gametes[edit | edit source]
The gametes of polyploids are unusual, because they may carry several sets of chromosomes. For example, common wheat is a polyploid with six sets of chromosomes, two sets coming originally from each of three different species. So there are six sets of chromosomes in most cells, and three sets of chromosomes in the gametes.
Related pages[edit | edit source]
- Aneuploidy, one or a few chromosomes more or less than the usual number in the species
References[edit | edit source]
- ↑ Gregory T.R. & Mable, B.K. 2005. Polyploidy in animals. In The Evolution of the Genome ed T.R. Gregory. Elsevier, San Diego. 427–517.
- ↑
- ↑
- ↑ Wood, Troy E. et al. 2009. The frequency of polyploid speciation in vascular plants. PNAS 106, 32
- ↑ Tate J.A. Soltis D.E. & Soltis P.S. 2005. Polyploidy in plants. In The Evolution of the Genome ed T.R. Gregory. Elsevier, San Diego. 371–426.
- ↑ White M.J.D. 1973. The chromosomes. 6th ed, Chapman & Hall, London. p28
- ↑ Stebbins G.L. 1950. Variation and evolution in plants. Chapter XII: The Karyotype. Columbia University Press N.Y.
- ↑
Related pages[edit | edit source]
This article is a stub. You can help WikiMD by registering to expand it. |
Search WikiMD
Ad.Tired of being Overweight? Try W8MD's physician weight loss program.
Semaglutide (Ozempic / Wegovy and Tirzepatide (Mounjaro / Zepbound) available.
Advertise on WikiMD
WikiMD's Wellness Encyclopedia |
Let Food Be Thy Medicine Medicine Thy Food - Hippocrates |
Translate this page: - East Asian
中文,
日本,
한국어,
South Asian
हिन्दी,
தமிழ்,
తెలుగు,
Urdu,
ಕನ್ನಡ,
Southeast Asian
Indonesian,
Vietnamese,
Thai,
မြန်မာဘာသာ,
বাংলা
European
español,
Deutsch,
français,
Greek,
português do Brasil,
polski,
română,
русский,
Nederlands,
norsk,
svenska,
suomi,
Italian
Middle Eastern & African
عربى,
Turkish,
Persian,
Hebrew,
Afrikaans,
isiZulu,
Kiswahili,
Other
Bulgarian,
Hungarian,
Czech,
Swedish,
മലയാളം,
मराठी,
ਪੰਜਾਬੀ,
ગુજરાતી,
Portuguese,
Ukrainian
Medical Disclaimer: WikiMD is not a substitute for professional medical advice. The information on WikiMD is provided as an information resource only, may be incorrect, outdated or misleading, and is not to be used or relied on for any diagnostic or treatment purposes. Please consult your health care provider before making any healthcare decisions or for guidance about a specific medical condition. WikiMD expressly disclaims responsibility, and shall have no liability, for any damages, loss, injury, or liability whatsoever suffered as a result of your reliance on the information contained in this site. By visiting this site you agree to the foregoing terms and conditions, which may from time to time be changed or supplemented by WikiMD. If you do not agree to the foregoing terms and conditions, you should not enter or use this site. See full disclaimer.
Credits:Most images are courtesy of Wikimedia commons, and templates Wikipedia, licensed under CC BY SA or similar.
Contributors: Kondreddy Naveen