- "Haplo" redirects here. For the fictional character, see The Death Gate Cycle. The Death Gate Cycle is a seven-part series of Fantasy novels written by Margaret Weis and Tracy Hickman.
Ploidy is the number of homologous sets of chromosomes in a biological cell. Homologous chromosomes are Chromosomes in a Biological cell that pair ( synapse) during Meiosis, or alternatively non-identical chromosomes that The cell is the structural and functional unit of all known living Organisms It is the smallest unit of an organism that is classified as living and is often called 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. A spermatozoon or spermatozoan ( pl spermatozoa) from the Ancient Greek σπέρμα (seed and ζῷον (living being and more commonly known An ovum (plural ova) is a Haploid Female reproductive cell or Gamete. 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. Polyploidy occurs in cells and Organisms when there are more than two homologous sets of Chromosomes. Plants are living Organisms belonging to the kingdom Plantae. Prehistoric amphibian Amphibians (class Amphibia such as Frogs Toads Salamanders Newts Gymnophiona, Sirens and Reptiles, or members of the class Reptilia are air-breathing Cold-blooded Vertebrates that have skin covered in scales as opposed to hair or feathers Insects ( Class Insecta) are a major group of Arthropods and the most diverse group of Animals on the Earth with over a million described
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. A sex-determination system is a biological system that determines the development of sexual characteristics in an Organism. For example, a human cell has 46 chromosomes, which is an integer multiple of the monoploid number, 23. The integers (from the Latin integer, literally "untouched" hence "whole" the word entire comes from the same origin but via French 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. Aneuploidy is defined as an abnormal number of Chromosomes Syndromes caused by an extra or missing chromosome are among the most widely recognized Genetic disorders In humans, examples include having a single extra chromosome (such as Down syndrome), or missing a chromosome (such as Turner syndrome). Down syndrome, Down's syndrome, or trisomy 21 is a Chromosomal disorder caused by the presence of all or part of an extra 21st chromosome. Turner syndrome or Ullrich-Turner syndrome encompasses several conditions of which monosomy X is the most common Aneuploidy is not normally considered -ploidy but -somy, such as trisomy or monosomy.
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Haploid and Monoploid
The haploid number is the number of chromosomes in a gamete of an individual. A gamete (from Ancient Greek γαμέτης; translated gamete = wife gametes = husband is a cell that fuses with another gamete This is distinct from the monoploid number which is the number of unique chromosomes in a single complete set.
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. Common wheat, Triticum aestivum, (also known as bread wheat) is a cultivated wheat species Polyploidy occurs in cells and Organisms when there are more than two homologous sets of Chromosomes. 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). "Somatic" redirects here for the musician known as Somatic see Hahn Rowe.
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. A fungus (ˈfʌŋgəs is a eukaryotic Organism that is a member of the kingdom Fungi (ˈfʌndʒaɪ Algae ( sing. alga are a large and diverse group of simple typically Autotrophic organisms ranging from Unicellular to Multicellular forms The Australian bulldog ant, Myrmecia pilosula, a haplodiploid species has n = 1, the lowest known (and lowest theoretically possible) n. The jack jumper ant, hopper ant or jumper ant, Myrmecia pilosula, is a species of Bulldog ant that is native to Australia. 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.
Plants and some algae switch between a haploid and a diploid or polyploid state, with one of the stages emphasized over the other. Plants are living Organisms belonging to the kingdom Plantae. Polyploidy occurs in cells and Organisms when there are more than two homologous sets of Chromosomes. This is called alternation of generations. The Alternation of phases (or generations) describes the life cycle of Plants Fungi and Protists A multicellular Diploid phase alternates 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. For other meanings see Zygote (disambiguation. A zygote (from Greek ζυγωτός zugōtos "joined" or "yoked" During meiosis, germ cell precursors have their number of chromosomes halved by randomly "choosing" one homologue, resulting in haploid germ cells (sperm and ovum). In Biology or life science meiosis (pronounced my-oh-sis is a process of reductional division in which the number of chromosomes per cell is cut in half The term sperm is derived from the Greek word (σπέρμα sperma (meaning "seed" and refers to the male reproductive cells. An ovum (plural ova) is a Haploid Female reproductive cell or Gamete.
Diploid
Diploid cells have two homologous copies of each chromosome, usually one from the mother and one from the father. Homologous chromosomes are Chromosomes in a Biological cell that pair ( synapse) during Meiosis, or alternatively non-identical chromosomes that A chromosome is an organized structure of DNA and Protein that is found in cells. "Mom" "Mum" and "Mommy" redirect here The father is defined as the Male Parent of an offspring The Adjective "paternal" refers to father parallel to "maternal" for 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). Aneuploidy is defined as an abnormal number of Chromosomes Syndromes caused by an extra or missing chromosome are among the most widely recognized Genetic disorders 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.
Retroviruses that contain two copies of their RNA genome in each viral particle are also said to be diploid. A retrovirus is any Virus belonging to the viral family Retroviridae. Examples include human foamy virus, human T-lymphotropic virus, and HIV. Human foamy virus (HFV is a VI Spumavirus virus also known as spumaretrovirus Human T-lymphotropic virus (HTLV is a Human, single-stranded RNA Retrovirus that causes T-cell Leukemia and T-cell Lymphoma Human immunodeficiency virus ( HIV) is a Lentivirus (a member of the Retrovirus family that can lead to acquired immunodeficiency syndrome [1]
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. Mammals ( class Mammalia) are a class of Vertebrate Animals characterized by the presence of Sweat glands, including sweat glands A spermatozoon or spermatozoan ( pl spermatozoa) from the Ancient Greek σπέρμα (seed and ζῷον (living being and more commonly known An ovum (plural ova) is a Haploid Female reproductive cell or Gamete. This was one of the procedures used by Japanese researchers to produce Kaguya, a fatherless mouse. For a topic outline on this subject see List of basic Japan topics. Kaguya is a Mouse that has two parents of the same sex She was named after a Japanese folk tale in which the moon-born princess Kaguya ( Kaguya-hime) is A mouse (plural mice) is a small Animal that belongs to one
Haploidisation sometimes occurs in plants when meiotically reduced cells (usually egg cells) develop by parthenogenesis.
Polyploidy
Polyploidy is the state where all cells have multiple pairs of chromosomes beyond the basic set. Polyploidy occurs in cells and Organisms when there are more than two homologous sets of Chromosomes. 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. The Triangle of U is a theory about the evolution and relationships between members of the Plant Genus Brassica. Polyploid plants are probably most often formed from the pairing of meiotically unreduced gametes (Ramsey and Schemske, 2002). A gamete (from Ancient Greek γαμέτης; translated gamete = wife gametes = husband is a cell that fuses with another gamete
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). Somatic cells are any cells forming the body of an organism as opposed to Germline cells Endoreduplication is the duplication of the Genome without Mitosis. In classical genetics the genome of a Diploid Organism including Eukarya refers to a full set of chromosomes or genes in a Gamete, thereby Mitosis is the process in which a Eukaryotic cell separates the Chromosomes in its Cell nucleus, into two identical sets in two daughter nuclei
The extreme in polyploidy occurs in the fern-ally 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. Ophioglossum ( Adder's-tongue) is a genus of about 25-30 species of Ophioglossales in the family Ophioglossaceae, with a Interestingly, these plants seem to have simplified structures in their phenotype.
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. The prokaryotes (proʊˈkærioʊts singular prokaryote /proʊˈkæriət/ are a group of Organisms that lack a Cell nucleus (= karyon or any other This is because under logarithmic growth conditions the cells are able to replicate their DNA faster than they can divide.
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.
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