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Encyclopedia > Ploidy

Ploidy is the number of homologous sets of chromosomes in a biological cell. The ploidy of cells can vary within an organism. In humans, most cells are diploid (containing one set of chromosomes from each parent), but sex cells (sperm and egg) are haploid. In contrast, tetraploidy (four sets of chromosomes) is a type of polyploidy and is common in plants, and not uncommon in amphibians, reptiles, and various species of insects. Homologous chromosomes are chromosomes in a biological cell that pair (synapse) during meiosis, or alternatively, non-identical chromosomes that contain information for the same biological features and contain the same genes at the same loci but possibly different genetic information, called alleles, at those genes. ... Cells in culture, stained for keratin The cell is the structural and functional unit of all living organisms. ... A spermatozoon or spermatozoan ( spermatozoa), from the ancient Greek σπέρμα (seed) and (living being) and more commonly known as a sperm cell, is the haploid cell that is the male gamete. ... A human ovum Sperm cells attempting to fertilize an ovum An ovum (plural ova) is a haploid female reproductive cell or gamete. ... Polyploidy refers to cells or organisms that contain more than two copies of each of their chromosomes. ... For other uses, see Plant (disambiguation). ... For other uses, see Amphibian (disambiguation). ... Reptilia redirects here. ... Orders Subclass Apterygota Archaeognatha (bristletails) Thysanura (silverfish) Subclass Pterygota Infraclass Paleoptera (Probably paraphyletic) Ephemeroptera (mayflies) Odonata (dragonflies and damselflies) Infraclass Neoptera Superorder Exopterygota Grylloblattodea (ice-crawlers) Mantophasmatodea (gladiators) Plecoptera (stoneflies) Embioptera (webspinners) Zoraptera (angel insects) Dermaptera (earwigs) Orthoptera (grasshoppers, etc) Phasmatodea (stick insects) Blattodea (cockroaches) Isoptera (termites) Mantodea (mantids) Psocoptera...


The number of chromosomes in one of the mutually-homologous sets is called the monoploid number (x). This is the same number for every set in every cell of a given organism.


Euploidy is the state of a cell or organism having an integral multiple of the monoploid number, possibly excluding the sex-determining chromosomes. For example, a human cell has 46 chromosomes, which is an integer multiple of the monoploid number, 23. A human with abnormal, but integral, multiples of this full set (e.g. 69 chromosomes) would also be considered as euploid. Aneuploidy is the state of not having euploidy. In humans, examples include having a single extra chromosome (such as Down syndrome), or missing a chromosome (such as Turner syndrome). Aneuploidy is not normally considered -ploidy but -somy, such as trisomy or monosomy. A sex-determination system is a biological system that determines the development of sexual characteristics in an organism. ... The integers are commonly denoted by the above symbol. ... Aneuploidy is a change in the number of chromosomes that can lead to a chromosomal disorder. ...

Contents

Haploid and Monoploid

The haploid number is the number of chromosomes in a gamete of an individual. This is distinct from the monoploid number which is the number of unique chromosomes in a single complete set. A gamete (from Ancient Greek γαμετης; translated gamete = wife, gametes = husband) is a cell that fuses with another gamete during fertilization (conception) in organisms that reproduce sexually. ...


In humans, the monoploid number (x) equals the haploid number (the number in a gamete, n), that is, x = n = 23. In some species (especially plants), these numbers differ. Commercial common wheat is an allopolyploid with six sets of chromosomes, two sets coming originally from each of three different species, with six copies of chromosomes in each cell. The gametes of common wheat are considered as haploid since they contain half the genetic information of somatic cells, but are not monoploid as they still contain three complete sets of chromosomes from the original three different species (n = 3x). Binomial name Triticum aestivum L. Common wheat (also known as bread wheat) is by far the most important wheat species in cultivation today. ... Polyploid (in Greek: πολλαπλόν - multiple) cells or organisms that contain more than two copies of each of their chromosomes. ... The term somatic refers to the body, as distinct from some other entity, such as the mind. ...


Most fungi and a few algae are monoploid organisms, and male bees, wasps, and ants are haploid because of the way they develop from unfertilized, haploid eggs. The Australian bulldog ant, Myrmecia pilosula, a haplodiploid species has n = 1, the lowest known n. A monoploid cell is likely to be identical to the cell it was copied from however in haploid cells one of two differing copies of the same chromosome is in the haploid set. For the fictional character, see Fungus the Bogeyman. ... A seaweed (Laurencia) up close: the branches are multicellular and only about 1 mm thick. ... Binomial name Myrmecia pilosula F. Smith, 1858 The jack jumper ant, hopper ant or jumper ant (Myrmecia pilosula) is a species of bulldog ant that is native to Australia. ... A haplodiploid species is one in which one of the sexes has haploid cells (cells containing one copy of each chromosome) and the other has diploid cells (cells containing two copies of each chromosome). ...


Plants and some algae switch between a haploid and a diploid or polyploid state, with one of the stages emphasized over the other. This is called alternation of generations. Most diploid organisms produce monoploid sex cells that can combine to form a diploid zygote, for example animals are primarily diploid but produce monoploid gametes. During meiosis, germ cell precursors have their number of chromosomes halved by randomly "choosing" one homologue, resulting in haploid germ cells (sperm and ovum). For other uses, see Plant (disambiguation). ... Polyploid (in Greek: πολλαπλόν - multiple) cells or organisms contain more than one copy (ploidy) of their chromosomes. ... Sporic or diplohaplontic life cycle. ... It has been suggested that Biparental zygote be merged into this article or section. ... For the figure of speech, see meiosis (figure of speech). ... For other uses, see Sperm (disambiguation). ... A human ovum Sperm cells attempting to fertilize an ovum An ovum (plural ova) is a haploid female reproductive cell or gamete. ...


Diploid

'Diploid (2') cells have two homologous copies of each chromosome, usually one from the mother and one from the father. The exact number of chromosomes may be one or two different from the 2 number yet the cell may still be classified as diploid (although with aneuploidy). Nearly all mammals are diploid organisms, although all individuals have some small fraction of cells that display polyploidy. Human diploid cells have 46 chromosomes and human haploid gametes (egg and sperm) have 23 chromosomes. Homologous chromosomes are chromosomes in a biological cell that pair (synapse) during meiosis, or alternatively, non-identical chromosomes that contain information for the same biological features and contain the same genes at the same loci but possibly different genetic information, called alleles, at those genes. ... A scheme of a condensed (metaphase) chromosome. ... Mom and Mommy redirect here. ... For other uses, see Father (disambiguation). ... Aneuploidy is a change in the number of chromosomes that can lead to a chromosomal disorder. ...


Haploidisation

Haploidisation (haploidization) is the process of creating a haploid cell (usually from a diploid cell).


A laboratory procedure called haploidisation forces a normal cell to expel half of its chromosomal complement. In mammals this renders this cell chromosomally equal to sperm or egg. This was one of the procedures used by Japanese researchers to produce Kaguya, a fatherless mouse. Orders Subclass Monotremata Monotremata Subclass Marsupialia Didelphimorphia Paucituberculata Microbiotheria Dasyuromorphia Peramelemorphia Notoryctemorphia Diprotodontia Subclass Placentalia Xenarthra Dermoptera Desmostylia Scandentia Primates Rodentia Lagomorpha Insectivora Chiroptera Pholidota Carnivora Perissodactyla Artiodactyla Cetacea Afrosoricida Macroscelidea Tubulidentata Hyracoidea Proboscidea Sirenia The mammals are the class of vertebrate animals primarily characterized by the presence of mammary... A spermatozoon or spermatozoan ( spermatozoa), from the ancient Greek σπέρμα (seed) and (living being) and more commonly known as a sperm cell, is the haploid cell that is the male gamete. ... A human ovum Sperm cells attempting to fertilize an ovum An ovum (plural ova) is a haploid female reproductive cell or gamete. ... Kaguya (born in 2004) is a mouse that has two parents of the same sex. ... This article is about the rodent. ...


Haploidisation sometimes occurs in plants when meiotically reduced cells (usually egg cells) develop by parthenogenesis.


Polyploidy

Main article: Polyploidy

Polyploidy is the state where all cells have multiple pairs of chromosomes beyond the basic set. These may be from the same species or from closely related species. In the latter case these are known as allopolyploids, amphidiploids or allotetraploids. Allopolyploids can be formed from the hybridisation of two separate species followed by their subsequent chromosome doubling. A good example is the so-called Brassica triangle where three different parent species have hybridized in each pair combination to form three different allopolyploid species. Polyploid plants are probably most often formed from the pairing of meiotically unreduced gametes (Ramsey and Schemske, 2002). Polyploidy refers to cells or organisms that contain more than two copies of each of their chromosomes. ... The Triangle of U is a theory which describes the evolution and relationships between members of the plant genus Brassica. ... Gametes (in Greek: γαμέτες) —also known as sex cells, germ cells, or spores—are the specialized cells that come together during fertilization (conception) in organisms that reproduce sexually. ...


Polyploidy occurs commonly in plants, but rarely in animals. Even in diploid organisms many somatic cells are polyploid due to a process called endoreduplication where duplication of the genome occurs without mitosis (cell division) This article does not cite any references or sources. ... Endoreduplication is the duplication of the genome without mitosis. ... In biology the genome of an organism is the whole hereditary information of an organism that is encoded in the DNA (or, for some viruses, RNA). ... Mitosis divides genetic information during cell division. ...


Variable or indefinite ploidy

Depending on growth conditions, prokaryotes such as bacteria may have a chromosome copy number of 1 to 4, and that number is commonly fractional, counting portions of the chromosome partly replicated at a given time. This is because under logarithmic growth conditions the cells are able to replicate their DNA faster than they can divide. Prokaryotes are unicellular (in rare cases, multicellular) organisms without a nucleus. ...


Mixoploidy

Mixoploidy refers to the presence of two cell lines, one diploid and one polyploid. Though polyploidy in humans is not viable, mixoploidy has been found in live adults and children. There are two types: diploid-triploid mixoploidy, in which some cells have 46 chromosomes and some have 69, and diploid-tetraploid mixoploidy, in which some cells have 46 and some have 92 chromosomes.


Dihaploidy and Polyhaploidy

Dihaploid and polyhaploid cells are formed by haploidisation of polyploids, i.e., by halving the chromosome constitution.


Dihaploids (which are diploid) are important for selective breeding of tetraploid crop plants (notably potatoes), because selection is faster with diploids than with tetraploids. Tetraploids can be reconstituted from the diploids, for example by somatic fusion.


The term “dihaploid” was coined by Bender (1963) to combine in one word the number of genome copies (diploid) and their origin (haploid). The term is well established in this original sense (e.g., Nogler 1984; Pehu 1996), but it has also been used for doubled monoploids or doubled haploids, which are homozygous and used for genetic research (Sprague et al, 1960).


References

  • Bender, K. 1963. “Über die Erzeugung und Enstehung dihaploider Pflanzen bei Solanum tuberosum”. Zeitschrift für Pflanzenzüchtung 50: 141–166.
  • Griffiths, A. J. et al. 2000. An introduction to genetic analysis, 7th ed. W. H. Freeman, New York ISBN 0-7167-3520-2
  • Nogler, G.A. 1984. Gametophytic apomixis. In Embryology of angiosperms. Edited by B.M. Johri. Springer, Berlin, Germany. pp. 475–518.
  • Pehu, E. 1996. The current status of knowledge on the cellular biology of potato. Potato Research 39: 429–435.
  • Ramsey, J., and Schemske, D.W. 2002. "Neopolyploidy in flowering plants". Annual Review of Ecology and Systematics 33: 589–639.
  • Sprague, G.F., Russell, W.A., and Penny, L.H. 1960. Mutations affecting quantitative traits in the selfed progeny of double monoploid maize stocks. Genetics 45(7): 855–866.
This article is about the general scientific term. ... A scheme of a condensed (metaphase) chromosome. ... Karyogram of human male using Giemsa staining. ... For the figure of speech, see meiosis (figure of speech). ... An autosome is a non-sex chromosome. ... A sex-determination system is a biological system that determines the development of sexual characteristics in an organism. ... An inversion is a chromosome rearrangement in which a segment of a chromosome is reversed end to end. ... Chromosomal translocation of the 4th and 20th chromosome. ... Polyploidy refers to cells or organisms that contain more than two copies of each of their chromosomes. ... // Overview Polyploid (in Greek: πολλαπλόν - multiple) cells or organisms contain more than two copies (ploidy) of their chromosomes. ... Chromatin is the complex of DNA and protein found inside the nuclei of eukaryotic cells. ... Euchromatin is a lightly packed form of chromatin that is rich in gene concentration, and is often (but not always) under active transcription. ... For differently-colored eyes, see Heterochromia. ... A nucleosome is a unit made of DNA and histones. ... Schematic representation of the assembly of the core histones into the nucleosome. ... Histone H1 is one of the 5 main histone proteins involved in the structure of chromatin in eukaryotic cells. ... Histone H2A is one of the 5 main histone proteins involved in the structure of chromatin in eukaryotic cells. ... Histone H2B is one of the 5 main histone proteins involved in the structure of chromatin in eukaryotic cells. ... H3 (Histone H3) is one of the 5 main histone proteins involved in the structure of chromatin in eukaryotic cells. ... H4 (Histone H4) is one of the 5 main histone proteins involved in the structure of chromatin in eukaryotic cells. ... Chromosome. ... A telomere is a region of highly repetitive DNA at the end of a linear chromosome that functions as a disposable buffer. ... A chromatid forms one part of a chromosome after it has coalesced for the process of mitosis or meiosis. ...

  Results from FactBites:
 
Ploidy Analysis: Encyclopedia of Cancer (922 words)
Ploidy analysis is a test that measures the amount of DNA in tumor cells.
DNA ploidy analysis is used in addition to the traditional grading system as another way to evaluate how malignant a tumor might be.
Ploidy analysis is performed on a sample of the tumor to determine how many of the cells have the normal amount of DNA and how many have more or less than the normal amount (called aneuploid).
VALIDITY OF FLOW CYTOMETRY FOR TESTING PLOIDY LEVEL IN RYEGRASSES (2503 words)
Cultivars pure in ploidy level are necessary because crossing among plants with different ploidy levels may result in genomic instability and uneven numbers of chromosomes, often leading to infertility and lower seed yields.
Ploidy level was determined based on position of the G1 peaks of unknowns in relation to the internal standard G1 peak.
The major phases are present regardless of ploidy level, but tetraploid plants, having twice the DNA complement and number of chromosomes, have peaks at double that of their diploid counterparts.
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