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chromosome
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{{pp-pc1}}{{short description|DNA molecule containing genetic material of a cell }}{{technical|date=April 2017}}File:Chromosome.svg|thumb|250px|Diagram of a replicated and condensed metaphase eukaryotic chromosome. (1) Chromatid â€“ one of the two identical parts of the chromosome after S phase. (2) CentromereCentromereA chromosome is a deoxyribonucleic acid (DNA) molecule with part or all of the genetic material (genome) of an organism. Most eukaryotic chromosomes include packaging proteins which, aided by chaperone proteins, bind to and condense the DNA molecule to prevent it from becoming an unmanageable tangle.JOURNAL, Hammond CM, Strømme CB, Huang H, Patel DJ, Groth A, Histone chaperone networks shaping chromatin function, Nature Reviews. Molecular Cell Biology, 18, 3, 141–158, March 2017, 28053344, 5319910, 10.1038/nrm.2016.159, BOOK, Wilson, John, Molecular biology of the cell : a problems approach, Garland Science, New York, 2002, 978-0-8153-3577-1, Chromosomes are normally visible under a light microscope only when the cell is undergoing the metaphase of cell division (where all chromosomes are aligned in the center of the cell in their condensed form).BOOK, Alberts, Bruce, Bray, Dennis, Hopkin, Karen, Johnson, Alexander, Lewis, Julian, Raff, Martin, Roberts, Keith, Walter, Peter, vanc, Essential Cell Biology, 2014, Garland Science, New York, NY, USA, 978-0-8153-4454-4, 621–626, Fourth, Before this happens, every chromosome is copied once (S phase), and the copy is joined to the original by a centromere, resulting either in an X-shaped structure (pictured to the right) if the centromere is located in the middle of the chromosome or a two-arm structure if the centromere is located near one of the ends. The original chromosome and the copy are now called sister chromatids. During metaphase the X-shape structure is called a metaphase chromosome. In this highly condensed form chromosomes are easiest to distinguish and study.BOOK,weblink Microscopical researches into the accordance in the structure and growth of animals and plants, Schleyden, M. J., 1847, In animal cells, chromosomes reach their highest compaction level in anaphase during chromosome segregation.JOURNAL, Antonin W, Neumann H, Chromosome condensation and decondensation during mitosis, Current Opinion in Cell Biology, 40, 15–22, June 2016, 26895139, 10.1016/j.ceb.2016.01.013, Chromosomal recombination during meiosis and subsequent sexual reproduction play a significant role in genetic diversity. If these structures are manipulated incorrectly, through processes known as chromosomal instability and translocation, the cell may undergo mitotic catastrophe. Usually, this will make the cell initiate apoptosis leading to its own death, but sometimes mutations in the cell hamper this process and thus cause progression of cancer.Some use the term chromosome in a wider sense, to refer to the individualized portions of chromatin in cells, either visible or not under light microscopy. Others use the concept in a narrower sense, to refer to the individualized portions of chromatin during cell division, visible under light microscopy due to high condensation.

Etymology

The word chromosome ({{IPAc-en|ˈ|k|r|oʊ|m|ə|ˌ|s|oʊ|m|,_|-|ˌ|z|oʊ|m}}{{Citation |last=Jones |first=Daniel |author-link=Daniel Jones (phonetician) |title=English Pronouncing Dictionary |editor=Peter Roach |editor2=James Hartmann |editor3=Jane Setter |place=Cambridge |publisher=Cambridge University Press |orig-year=1917 |year=2003 |isbn=978-3-12-539683-8 }}{{MerriamWebsterDictionary|Chromosome}}) comes from the Greek (chroma, "colour") and (soma, "body"), describing their strong staining by particular dyes.BOOK, Biological Stains - A Handbook on the Nature and Uses of the Dyes Employed in the Biological Laboratory, Coxx, H. J., Commission on Standardization of Biological Stains, 1925,weblink The term was coined by von Waldeyer-Hartz,JOURNAL, Waldeyer-Hartz, 1888, Über Karyokinese und ihre Beziehungen zu den Befruchtungsvorgängen, Archiv für Mikroskopische Anatomie und Entwicklungsmechanik, 32, 27, referring to the term chromatin, which was introduced by Walther Flemming.Some of the early karyological terms have become outdated.JOURNAL, Garbari, Fabio, Bedini, Gianni, Peruzzi, Lorenzo, vanc, 2012, Chromosome numbers of the Italian flora. From the Caryologia foundation to present, Caryologia - International Journal of Cytology, Cytosystematics and Cytogenetics, 65, 1, 65–66, 10.1080/00087114.2012.678090, JOURNAL, Peruzzi L, Garbari F, Bedini G, 2012, New trends in plant cytogenetics and cytoembryology: Dedicated to the memory of Emilio Battaglia, Plant Biosystems - an International Journal Dealing, 146, 3, 674–675, 10.1080/11263504.2012.712553, 2019-03-04, For example, Chromatin (Flemming 1880) and Chromosom (Waldeyer 1888), both ascribe color to a non-colored state.JOURNAL, Battaglia, Emilio, 2009, Caryoneme alternative to chromosome and a new caryological nomenclature, Caryologia - International Journal of Cytology, Cytosystematics, 62, 4, 1–80,weblink 2017-11-06,

History of discovery

{{double image|right|Walter sutton.jpg|140|Theodor Boveri.jpg|120|Walter Sutton (left) and Theodor Boveri (right) independently developed the chromosome theory of inheritance in 1902.}}The German scientists Schleiden, Virchow and Bütschli were among the first scientists who recognized the structures now familiar as chromosomes.JOURNAL, Fokin SI, 2013, Otto Bütschli (1848–1920) Where we will genuflect?,weblink Protistology, 8, 1, 22–35, In a series of experiments beginning in the mid-1880s, Theodor Boveri gave the definitive demonstration that chromosomes are the vectors of heredity; his two principles were the continuity of chromosomes and the individuality of chromosomes.{{Citation needed|date=April 2009}}{{explain|date=October 2015}} It is the second of these principles that was so original.{{Citation needed|date=April 2009}} Wilhelm Roux suggested that each chromosome carries a different genetic load. Boveri was able to test and confirm this hypothesis. Aided by the rediscovery at the start of the 1900s of Gregor Mendel's earlier work, Boveri was able to point out the connection between the rules of inheritance and the behaviour of the chromosomes. Boveri influenced two generations of American cytologists: Edmund Beecher Wilson, Nettie Stevens, Walter Sutton and Theophilus Painter were all influenced by Boveri (Wilson, Stevens, and Painter actually worked with him).BOOK, Carlson, Elof A., Mendel's Legacy: The Origin of Classical Genetics, Cold Spring Harbor, NY, Cold Spring Harbor Laboratory Press, 88, 2004, 978-087969675-7,weblink In his famous textbook The Cell in Development and Heredity, Wilson linked together the independent work of Boveri and Sutton (both around 1902) by naming the chromosome theory of inheritance the Boveri–Sutton chromosome theory (the names are sometimes reversed).Wilson, E.B. (1925). The Cell in Development and Heredity, Ed. 3. Macmillan, New York. p. 923. Ernst Mayr remarks that the theory was hotly contested by some famous geneticists: William Bateson, Wilhelm Johannsen, Richard Goldschmidt and T.H. Morgan, all of a rather dogmatic turn of mind. Eventually, complete proof came from chromosome maps in Morgan's own lab.Mayr, E. (1982). The growth of biological thought. Harvard. p. 749.The number of human chromosomes was published in 1923 by Theophilus Painter. By inspection through the microscope, he counted 24 pairs, which would mean 48 chromosomes. His error was copied by others and it was not until 1956 that the true number, 46, was determined by Indonesia-born cytogeneticist Joe Hin Tjio.WEB
, The bizarre case of the chromosome that never was
, Robert
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, 13 July 2013
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,weblink" title="web.archive.org/web/20131215103947weblink">weblink
, 15 December 2013
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Prokaryotes

The prokaryotes â€“ bacteria and archaea â€“ typically have a single circular chromosome, but many variations exist.JOURNAL, Thanbichler M, Shapiro L, Chromosome organization and segregation in bacteria, Journal of Structural Biology, 156, 2, 292–303, November 2006, 16860572, 10.1016/j.jsb.2006.05.007, The chromosomes of most bacteria, which some authors prefer to call genophores, can range in size from only 130,000 base pairs in the endosymbiotic bacteria Candidatus Hodgkinia cicadicolaJOURNAL, Van Leuven JT, Meister RC, Simon C, McCutcheon JP, Sympatric speciation in a bacterial endosymbiont results in two genomes with the functionality of one, Cell, 158, 6, 1270–1280, September 2014, 25175626, 10.1016/j.cell.2014.07.047, and Candidatus Tremblaya princeps,JOURNAL, McCutcheon JP, von Dohlen CD, An interdependent metabolic patchwork in the nested symbiosis of mealybugs, Current Biology, 21, 16, 1366–72, August 2011, 21835622, 3169327, 10.1016/j.cub.2011.06.051, to more than 14,000,000 base pairs in the soil-dwelling bacterium Sorangium cellulosum.JOURNAL, Han K, Li ZF, Peng R, Zhu LP, Zhou T, Wang LG, Li SG, Zhang XB, Hu W, Wu ZH, Qin N, Li YZ, Extraordinary expansion of a Sorangium cellulosum genome from an alkaline milieu, Scientific Reports, 3, 2101, 2013, 23812535, 3696898, 10.1038/srep02101, 2013NatSR...3E2101H, Spirochaetes of the genus Borrelia are a notable exception to this arrangement, with bacteria such as Borrelia burgdorferi, the cause of Lyme disease, containing a single linear chromosome.JOURNAL, Hinnebusch J, Tilly K, Linear plasmids and chromosomes in bacteria, Molecular Microbiology, 10, 5, 917–22, December 1993, 7934868, 10.1111/j.1365-2958.1993.tb00963.x,

Structure in sequences

Prokaryotic chromosomes have less sequence-based structure than eukaryotes. Bacteria typically have a one-point (the origin of replication) from which replication starts, whereas some archaea contain multiple replication origins.JOURNAL, Kelman LM, Kelman Z, Multiple origins of replication in archaea, Trends in Microbiology, 12, 9, 399–401, September 2004, 15337158, 10.1016/j.tim.2004.07.001, The genes in prokaryotes are often organized in operons, and do not usually contain introns, unlike eukaryotes.

DNA packaging

Prokaryotes do not possess nuclei. Instead, their DNA is organized into a structure called the nucleoid.JOURNAL, Thanbichler M, Wang SC, Shapiro L, The bacterial nucleoid: a highly organized and dynamic structure, Journal of Cellular Biochemistry, 96, 3, 506–21, October 2005, 15988757, 10.1002/jcb.20519, JOURNAL, Le TB, Imakaev MV, Mirny LA, Laub MT, High-resolution mapping of the spatial organization of a bacterial chromosome, Science, 342, 6159, 731–4, November 2013, 24158908, 3927313, 10.1126/science.1242059, 2013Sci...342..731L, The nucleoid is a distinct structure and occupies a defined region of the bacterial cell. This structure is, however, dynamic and is maintained and remodeled by the actions of a range of histone-like proteins, which associate with the bacterial chromosome.JOURNAL, Sandman K, Pereira SL, Reeve JN, Diversity of prokaryotic chromosomal proteins and the origin of the nucleosome, Cellular and Molecular Life Sciences, 54, 12, 1350–64, December 1998, 9893710, 10.1007/s000180050259, In archaea, the DNA in chromosomes is even more organized, with the DNA packaged within structures similar to eukaryotic nucleosomes.JOURNAL, Sandman K, Reeve JN, Structure and functional relationships of archaeal and eukaryal histones and nucleosomes, Archives of Microbiology, 173, 3, 165–9, March 2000, 10763747, 10.1007/s002039900122, JOURNAL, Pereira SL, Grayling RA, Lurz R, Reeve JN, Archaeal nucleosomes, Proceedings of the National Academy of Sciences of the United States of America, 94, 23, 12633–7, November 1997, 9356501, 25063, 10.1073/pnas.94.23.12633, 1997PNAS...9412633P, Certain bacteria also contain plasmids or other extrachromosomal DNA. These are circular structures in the cytoplasm that contain cellular DNA and play a role in horizontal gene transfer. In prokaryotes (see nucleoids) and viruses,JOURNAL, Johnson JE, Chiu W, Structures of virus and virus-like particles, Current Opinion in Structural Biology, 10, 2, 229–35, April 2000, 10753814, 10.1016/S0959-440X(00)00073-7, the DNA is often densely packed and organized; in the case of archaea, by homology to eukaryotic histones, and in the case of bacteria, by histone-like proteins.Bacterial chromosomes tend to be tethered to the plasma membrane of the bacteria. In molecular biology application, this allows for its isolation from plasmid DNA by centrifugation of lysed bacteria and pelleting of the membranes (and the attached DNA).Prokaryotic chromosomes and plasmids are, like eukaryotic DNA, generally supercoiled. The DNA must first be released into its relaxed state for access for transcription, regulation, and replication.

Eukaryotes

(File:Eukaryote DNA-en.svg|thumb|280px|Organization of DNA in a eukaryotic cell.){{See also|Eukaryotic chromosome fine structure}}Chromosomes in eukaryotes are composed of chromatin fiber. Chromatin fiber is made of nucleosomes (histone octamers with part of a DNA strand attached to and wrapped around it). Chromatin fibers are packaged by proteins into a condensed structure called chromatin. Chromatin contains the vast majority of DNA and a small amount inherited maternally, can be found in the mitochondria. Chromatin is present in most cells, with a few exceptions, for example, red blood cells.Chromatin allows the very long DNA molecules to fit into the cell nucleus. During cell division chromatin condenses further to form microscopically visible chromosomes. The structure of chromosomes varies through the cell cycle. During cellular division chromosomes are replicated, divided, and passed successfully to their daughter cells so as to ensure the genetic diversity and survival of their progeny. Chromosomes may exist as either duplicated or unduplicated. Unduplicated chromosomes are single double helixes, whereas duplicated chromosomes contain two identical copies (called chromatids or sister chromatids) joined by a centromere.File:Chromatin Structures.png|thumb|center|850px|The major structures in DNA compaction: DNA, the nucleosome, the 10 nm "beads-on-a-string" fibre, the 30 nm fibre and the metaphasemetaphaseEukaryotes (cells with nuclei such as those found in plants, fungi, and animals) possess multiple large linear chromosomes contained in the cell's nucleus. Each chromosome has one centromere, with one or two arms projecting from the centromere, although, under most circumstances, these arms are not visible as such. In addition, most eukaryotes have a small circular mitochondrial genome, and some eukaryotes may have additional small circular or linear cytoplasmic chromosomes.In the nuclear chromosomes of eukaryotes, the uncondensed DNA exists in a semi-ordered structure, where it is wrapped around histones (structural proteins), forming a composite material called chromatin.

Interphase chromatin

During interphase (the period of the cell cycle where the cell is not dividing), two types of chromatin can be distinguished:
  • Euchromatin, which consists of DNA that is active, e.g., being expressed as protein.
  • Heterochromatin, which consists of mostly inactive DNA. It seems to serve structural purposes during the chromosomal stages. Heterochromatin can be further distinguished into two types:
    • Constitutive heterochromatin, which is never expressed. It is located around the centromere and usually contains repetitive sequences.
    • Facultative heterochromatin, which is sometimes expressed.

Metaphase chromatin and division

{{see also|mitosis|meiosis}}File:HumanChromosomesChromomycinA3.jpg|thumb|200px|right|Human chromosomes during metaphasemetaphaseIn the early stages of mitosis or meiosis (cell division), the chromatin double helix become more and more condensed. They cease to function as accessible genetic material (transcription stops) and become a compact transportable form. This compact form makes the individual chromosomes visible, and they form the classic four arm structure, a pair of sister chromatids attached to each other at the centromere. The shorter arms are called p arms (from the French petit, small) and the longer arms are called q arms (q follows p in the Latin alphabet; q-g "grande"; alternatively it is sometimes said q is short for queue meaning tail in French"Chromosome Mapping: Idiograms" Nature Education - August 13, 2013). This is the only natural context in which individual chromosomes are visible with an optical microscope.Mitotic metaphase chromosomes are best described by a linearly organized longitudinally compressed array of consecutive chromatin loops.JOURNAL, Naumova N, Imakaev M, Fudenberg G, Zhan Y, Lajoie BR, Mirny LA, Dekker J, Organization of the mitotic chromosome, Science, 342, 6161, 948–53, November 2013, 24200812, 4040465, 10.1126/science.1236083, 2013Sci...342..948N, During mitosis, microtubules grow from centrosomes located at opposite ends of the cell and also attach to the centromere at specialized structures called kinetochores, one of which is present on each sister chromatid. A special DNA base sequence in the region of the kinetochores provides, along with special proteins, longer-lasting attachment in this region. The microtubules then pull the chromatids apart toward the centrosomes, so that each daughter cell inherits one set of chromatids. Once the cells have divided, the chromatids are uncoiled and DNA can again be transcribed. In spite of their appearance, chromosomes are structurally highly condensed, which enables these giant DNA structures to be contained within a cell nucleus.

Human chromosomes

Chromosomes in humans can be divided into two types: autosomes (body chromosome(s)) and allosome (sex chromosome(s)). Certain genetic traits are linked to a person's sex and are passed on through the sex chromosomes. The autosomes contain the rest of the genetic hereditary information. All act in the same way during cell division. Human cells have 23 pairs of chromosomes (22 pairs of autosomes and one pair of sex chromosomes), giving a total of 46 per cell. In addition to these, human cells have many hundreds of copies of the mitochondrial genome. Sequencing of the human genome has provided a great deal of information about each of the chromosomes. Below is a table compiling statistics for the chromosomes, based on the Sanger Institute's human genome information in the Vertebrate Genome Annotation (VEGA) database.Vega.sanger.ad.uk, all data in this table was derived from this database, November 11, 2008. Number of genes is an estimate, as it is in part based on gene predictions. Total chromosome length is an estimate as well, based on the estimated size of unsequenced heterochromatin regions.(File:Genes and base pairs on chromosomes.svg|frame|Estimated number of genes and base pairs (in mega base pairs) on each human chromosome){| class="wikitable sortable" style="text-align:right"|+! Chromosome !! GenesWEB,weblink Ensembl genome browser 71: Homo sapiens – Chromosome summary – Chromosome 1: 1–1,000,000, apr2013.archive.ensembl.org, 2016-04-11, !! Total base pairs !! % of bases !! Sequenced base pairsSequenced percentages are based on fraction of euchromatin portion, as the Human Genome Project goals called for determination of only the euchromatic portion of the genome. Telomeres, centromeres, and other heterochromatic regions have been left undetermined, as have a small number of unclonable gaps. Seeweblink for more information on the Human Genome Project.!% sequenced base pairs
Chromosome 1 (human)>1 2000 247,199,719 8.0 224,999,719 |91.02%
Chromosome 2 (human)>2 1300 242,751,149 7.9 237,712,649 |97.92%
Chromosome 3 (human)>3 1000 199,446,827 6.5 194,704,827 |97.62%
Chromosome 4 (human)>4 1000 191,263,063 6.2 187,297,063 |97.93%
Chromosome 5 (human)>5 900 180,837,866 5.9 177,702,766 |98.27%
Chromosome 6 (human)>6 1000 170,896,993 5.5 167,273,993 |97.88%
Chromosome 7 (human)>7 900 158,821,424 5.2 154,952,424 |97.56%
Chromosome 8 (human)>8 700 146,274,826 4.7 142,612,826 |97.50%
Chromosome 9 (human)>9 800 140,442,298 4.6 120,312,298 |85.67%
Chromosome 10 (human)>10 700 135,374,737 4.4 131,624,737 |97.23%
Chromosome 11 (human)>11 1300 134,452,384 4.4 131,130,853 |97.53%
Chromosome 12 (human)>12 1100 132,289,534 4.3 130,303,534 |98.50%
Chromosome 13 (human)>13 300 114,127,980 3.7 95,559,980 |83.73%
Chromosome 14 (human)>14 800 106,360,585 3.5 88,290,585 |83.01%
Chromosome 15 (human)>15 600 100,338,915 3.3 81,341,915 |81.07%
Chromosome 16 (human)>16 800 88,822,254 2.9 78,884,754 |88.81%
Chromosome 17 (human)>17 1200 78,654,742 2.6 77,800,220 |98.91%
Chromosome 18 (human)>18 200 76,117,153 2.5 74,656,155 |98.08%
Chromosome 19 (human)>19 1500 63,806,651 2.1 55,785,651 |87.43%
Chromosome 20 (human)>20 500 62,435,965 2.0 59,505,254 |95.31%
Chromosome 21 (human)>21 200 46,944,323 1.5 34,171,998 |72.79%
Chromosome 22 (human)>22 500 49,528,953 1.6 34,893,953 |70.45%
X chromosome>X (sex chromosome) 800 154,913,754 5.0 151,058,754 |97.51%
Y chromosome>Y (sex chromosome) 50 57,741,652 1.9 25,121,652|43.51%
class="sortbottom"! Total ||style="text-align:right"| 21,000 ||style="text-align:right"| 3,079,843,747 ||style="text-align:right"| 100.0 ||style="text-align:right"| 2,857,698,560|92.79%

Number in various organisms

In eukaryotes

These tables give the total number of chromosomes (including sex chromosomes) in a cell nucleus. For example, most eukaryotes are diploid, like humans who have 22 different types of autosomes, each present as two homologous pairs, and two sex chromosomes. This gives 46 chromosomes in total. Other organisms have more than two copies of their chromosome types, such as bread wheat, which is hexaploid and has six copies of seven different chromosome types â€“ 42 chromosomes in total.{| border="0"{| class="wikitable sortable" style="float:left; margin:1em 0 1em 1em"|+ Chromosome numbers in some plants! Plant Species !! #
Arabidopsis thaliana (diploid)ARMSTRONG SJ, JONES GH JOURNAL = JOURNAL OF EXPERIMENTAL BOTANY ISSUE = 380 DATE = JANUARY 2003 DOI = 10.1093/JXB/54.380.1, 10
Rye (diploid)GILL BS, KIMBER G JOURNAL = PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA ISSUE = 4 DATE = APRIL 1974 PMC = 388202 BIBCODE = 1974PNAS...71.1247G, 14
Einkorn wheat (diploid)DUBCOVSKY J, LUO MC, ZHONG GY, BRANSTEITTER R, DESAI A, KILIAN A, KLEINHOFS A, DVORáK J JOURNAL = GENETICS ISSUE = 2 DATE = JUNE 1996 PMC = 1207354, 14
Maize (diploid or palaeotetraploid)KATO A, LAMB JC, BIRCHLER JA JOURNAL = PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA ISSUE = 37 DATE = SEPTEMBER 2004 PMC = 518793 BIBCODE = 2004PNAS..10113554K, 20
Durum wheat (tetraploid) >| 28
Bread wheat (hexaploid) >| 42
Cultivated tobacco (tetraploid)KENTON A, PAROKONNY AS, GLEBA YY, BENNETT MD JOURNAL = MOLECULAR & GENERAL GENETICS ISSUE = 2 DATE = AUGUST 1993 DOI = 10.1007/BF00277053, 48
Ophioglossum>Adder's tongue fern (polyploid)LEITCH IJ, SOLTIS DE, SOLTIS PS, BENNETT MD > TITLE = EVOLUTION OF DNA AMOUNTS ACROSS LAND PLANTS (EMBRYOPHYTA) VOLUME = 95 PAGES = 207–17 PMID = 15596468 AUTHORLINK3 = PAMELA S. SOLTIS | approx. 1,200
{| class="wikitable sortable" style="float:left; margin:1em 0 1em 1em"|+ Chromosome numbers (2n) in some animals! Species !! #
Indian muntjac >| 7
Drosophila melanogaster>Common fruit fly 8
Pill millipede (Arthrosphaera fumosa)AMBARISH, C.N. SRIDHAR, K.R. DOI = 10.1080/00087114VOLUME=66 DATE=2014| 30
Earthworm (Octodrilus complanatus)VITTURI R, COLOMBA MS, PIRRONE AM, MANDRIOLI M JOURNAL = THE JOURNAL OF HEREDITY ISSUE = 4 DATE = 2002 DOI = 10.1093/JHERED/93.4.279, 36
Tibetan fox >| 36
Domestic catNIE W, WANG J, O'BRIEN PC, FU B, YING T, FERGUSON-SMITH MA, YANG F JOURNAL = CHROMOSOME RESEARCH ISSUE = 3 DATE = 2002 DOI = 10.1023/A:1015292005631, 38
Domestic pig >| 38
Laboratory mouseROMANENKO SA, PERELMAN PL, SERDUKOVA NA, TRIFONOV VA, BILTUEVA LS, WANG J, LI T, NIE W, O'BRIEN PC, VOLOBOUEV VT, STANYON R, FERGUSON-SMITH MA, YANG F, GRAPHODATSKY AS JOURNAL = MAMMALIAN GENOME ISSUE = 12 DATE = DECEMBER 2006 DOI = 10.1007/S00335-006-0081-Z, PAINTER TS > TITLE = A COMPARISON OF THE CHROMOSOMES OF THE RAT AND MOUSE WITH REFERENCE TO THE QUESTION OF CHROMOSOME HOMOLOGY IN MAMMALS VOLUME = 13 PAGES = 180–9 PMID = 17246549 | 40
Laboratory rat >| 42
Rabbit (Oryctolagus cuniculus)HAYES H, ROGEL-GAILLARD C, ZIJLSTRA C, DE HAAN NA, URIEN C, BOURGEAUX N, BERTAUD M, BOSMA AA JOURNAL = CYTOGENETIC AND GENOME RESEARCH ISSUE = 2–3 DATE = 2002 DOI = 10.1159/000069807, 44
Syrian hamster >| 44
Guppy (poecilia reticulata)HTTP://FANCYGUPPY.WEBS.COM/GENETICS.HTM ACCESS-DATE=2009-12-06, 46
Human >|46
HaresROBINSON TJ, YANG F, HARRISON WR JOURNAL = CYTOGENETIC AND GENOME RESEARCH ISSUE = 1–4 DATE = 2002 DOI = 10.1159/000063034, {{citation title=Rabbits, Hares and Pikas. Status Survey and Conservation Action Plan pages= 61–94 last1 = Chapman last2=Flux name-list-format = vanc | 48
Gorillas, Pan (genus)>chimpanzeesDE GROUCHY J > TITLE = CHROMOSOME PHYLOGENIES OF MAN, GREAT APES, AND OLD WORLD MONKEYS VOLUME = 73 PAGES = 37–52 PMID = 3333352 | 48
Domestic sheep >| 54
Garden snailVITTURI R, LIBERTINI A, SINEO L, SPARACIO I, LANNINO A, GREGORINI A, COLOMBA M JOURNAL = MICRON ISSUE = 4 DATE = 2005 DOI = 10.1016/J.MICRON.2004.12.010, 54
Bombyx mori>SilkwormYASUKOCHI Y, ASHAKUMARY LA, BABA K, YOSHIDO A, SAHARA K > TITLE = A SECOND-GENERATION INTEGRATED MAP OF THE SILKWORM REVEALS SYNTENY AND CONSERVED GENE ORDER BETWEEN LEPIDOPTERAN INSECTS VOLUME = 173 PAGES = 1319–28 PMID = 16547103 DOI = 10.1534/GENETICS.106.055541, 56
ElephantsHOUCK ML, KUMAMOTO AT, GALLAGHER DS, BENIRSCHKE K JOURNAL = CYTOGENETICS AND CELL GENETICS ISSUE = 3–4 DATE = 2001 DOI = 10.1159/000056992, 56
Cattle>Cow 60
Donkey >| 62
Guinea pigSEMBA U, UMEDA Y, SHIBUYA Y, OKABE H, TANASE S, YAMAMOTO T JOURNAL = INTERNATIONAL IMMUNOPHARMACOLOGY ISSUE = 10–11 DATE = OCTOBER 2004 DOI = 10.1016/J.INTIMP.2004.06.003 | 64
Horse >| 64
DogWAYNE RK, OSTRANDER EA JOURNAL = BIOESSAYS ISSUE = 3 DATE = MARCH 1999 DOI = 10.1002/(SICI)1521-1878(199903)21:33.0.CO;2-Z, 78
Hedgehog >| 90
GoldfishCIUDAD J, CID E, VELASCO A, LARA JM, AIJóN J, ORFAO A JOURNAL = CYTOMETRY ISSUE = 1 DATE = MAY 2002 DOI = 10.1002/CYTO.10100, 100-104
KingfisherBURT DW JOURNAL = CYTOGENETIC AND GENOME RESEARCH ISSUE = 1–4 DATE = 2002 DOI = 10.1159/000063018, 132
{| class="wikitable sortable" style="float:left; margin:1em 0 1em 1em"|+ Chromosome numbers in other organisms! Species !! LargeChromosomes !! IntermediateChromosomes !! Microchromosomes
Trypanosoma brucei >| ≈100
Domestic pigeon (Columba livia domestics)10.1266/JJG.44.163 DATE=1969 FIRST1=MASAHIRO FIRST2=TATSURO FIRST3=HACHIRO FIRST4=MICHIKO FIRST5=MOTOMICHI FIRST6=SAJIRO JOURNAL=THE JAPANESE JOURNAL OF GENETICS ISSUE=3 | 59-63
ChickenSMITH J, BURT DW JOURNAL = ANIMAL GENETICS ISSUE = 4 DATE = AUGUST 1998 DOI = 10.1046/J.1365-2052.1998.00334.X, 8 2 sex chromosomes 60
Normal members of a particular eukaryotic species all have the same number of nuclear chromosomes (see the table). Other eukaryotic chromosomes, i.e., mitochondrial and plasmid-like small chromosomes, are much more variable in number, and there may be thousands of copies per cell.File:PLoSBiol3.5.Fig1bNucleus46Chromosomes.jpg|thumb|200px|left|The 23 human chromosome territories during prometaphase in fibroblastfibroblastAsexually reproducing species have one set of chromosomes that are the same in all body cells. However, asexual species can be either haploid or diploid.Sexually reproducing species have somatic cells (body cells), which are diploid [2n] having two sets of chromosomes (23 pairs in humans with one set of 23 chromosomes from each parent), one set from the mother and one from the father. Gametes, reproductive cells, are haploid [n]: They have one set of chromosomes. Gametes are produced by meiosis of a diploid germ line cell. During meiosis, the matching chromosomes of father and mother can exchange small parts of themselves (crossover), and thus create new chromosomes that are not inherited solely from either parent. When a male and a female gamete merge (fertilization), a new diploid organism is formed.Some animal and plant species are polyploid [Xn]: They have more than two sets of homologous chromosomes. Plants important in agriculture such as tobacco or wheat are often polyploid, compared to their ancestral species. Wheat has a haploid number of seven chromosomes, still seen in some cultivars as well as the wild progenitors. The more-common pasta and bread wheat types are polyploid, having 28 (tetraploid) and 42 (hexaploid) chromosomes, compared to the 14 (diploid) chromosomes in the wild wheat.JOURNAL, Sakamura, Tetsu, 1918, Kurze Mitteilung über die Chromosomenzahlen und die Verwandtschaftsverhältnisse der Triticum-Arten, Shokubutsugaku Zasshi, 32, 379, 150–3, 10.15281/jplantres1887.32.379_150,

In prokaryotes

Prokaryote species generally have one copy of each major chromosome, but most cells can easily survive with multiple copies.Charlebois R.L. (ed) 1999. Organization of the prokaryote genome. ASM Press, Washington DC. For example, Buchnera, a symbiont of aphids has multiple copies of its chromosome, ranging from 10–400 copies per cell.JOURNAL, Komaki K, Ishikawa H, Genomic copy number of intracellular bacterial symbionts of aphids varies in response to developmental stage and morph of their host, Insect Biochemistry and Molecular Biology, 30, 3, 253–8, March 2000, 10732993, 10.1016/S0965-1748(99)00125-3, However, in some large bacteria, such as Epulopiscium fishelsoni up to 100,000 copies of the chromosome can be present.JOURNAL, Mendell JE, Clements KD, Choat JH, Angert ER, Extreme polyploidy in a large bacterium, Proceedings of the National Academy of Sciences of the United States of America, 105, 18, 6730–4, May 2008, 18445653, 2373351, 10.1073/pnas.0707522105, 2008PNAS..105.6730M, Plasmids and plasmid-like small chromosomes are, as in eukaryotes, highly variable in copy number. The number of plasmids in the cell is almost entirely determined by the rate of division of the plasmid â€“ fast division causes high copy number.

Karyotype

(File:NHGRI human male karyotype.png|thumb|right|200px|Karyogram of a human male)In general, the karyotype is the characteristic chromosome complement of a eukaryote species.BOOK, White, M. J. D., The chromosomes, Chapman and Hall, distributed by Halsted Press, New York, London, 1973, 28, 978-0-412-11930-9, 6th, The preparation and study of karyotypes is part of cytogenetics.Although the replication and transcription of DNA is highly standardized in eukaryotes, the same cannot be said for their karyotypes, which are often highly variable. There may be variation between species in chromosome number and in detailed organization.In some cases, there is significant variation within species. Often there is:
1. variation between the two sexes 2. variation between the germ-line and soma (between gametes and the rest of the body) 3. variation between members of a population, due to balanced genetic polymorphism 4. geographical variation between races 5. mosaics or otherwise abnormal individuals.
Also, variation in karyotype may occur during development from the fertilized egg.The technique of determining the karyotype is usually called karyotyping. Cells can be locked part-way through division (in metaphase) in vitro (in a reaction vial) with colchicine. These cells are then stained, photographed, and arranged into a karyogram, with the set of chromosomes arranged, autosomes in order of length, and sex chromosomes (here X/Y) at the end.Like many sexually reproducing species, humans have special gonosomes (sex chromosomes, in contrast to autosomes). These are XX in females and XY in males.

Historical note

{{see also|Argument from authority#Use in science}}Investigation into the human karyotype took many years to settle the most basic question: How many chromosomes does a normal diploid human cell contain? In 1912, Hans von Winiwarter reported 47 chromosomes in spermatogonia and 48 in oogonia, concluding an XX/XO sex determination mechanism.JOURNAL, von Winiwarter H, Études sur la spermatogenèse humaine, Archives de Biologie, 27, 93, 147–9, 1912, Painter in 1922 was not certain whether the diploid number of man is 46 or 48, at first favouring 46.JOURNAL, Painter TS, The spermatogenesis of man, Anat. Res., 23, 129, 1922, He revised his opinion later from 46 to 48, and he correctly insisted on humans having an XX/XY system.JOURNAL, Painter, Theophilus S., Studies in mammalian spermatogenesis. II. The spermatogenesis of man, Journal of Experimental Zoology, April 1923, 37, 3, 291–336, 10.1002/jez.1400370303, New techniques were needed to definitively solve the problem:
  1. Using cells in culture
  2. Arresting mitosis in metaphase by a solution of colchicine
  3. Pretreating cells in a hypotonic solution 0.075 M KCl, which swells them and spreads the chromosomes
  4. Squashing the preparation on the slide forcing the chromosomes into a single plane
  5. Cutting up a photomicrograph and arranging the result into an indisputable karyogram.
It took until 1954 before the human diploid number was confirmed as 46.JOURNAL, 10.1111/j.1601-5223.1956.tb03010.x, Tjio JH, Levan A, The chromosome number of man, Hereditas, 42, 1–6, 1956, 1–2, 10261/15776, JOURNAL, Ford CE, Hamerton JL, The chromosomes of man, Nature, 178, 4541, 1020–3, November 1956, 13378517, 10.1038/1781020a0, 1956Natur.178.1020F, Considering the techniques of Winiwarter and Painter, their results were quite remarkable.Hsu T.C. Human and mammalian cytogenetics: a historical perspective. Springer-Verlag, N.Y. p10: "It's amazing that he [Painter] even came close!" Chimpanzees, the closest living relatives to modern humans, have 48 chromosomes as do the other great apes: in humans two chromosomes fused to form chromosome 2.

Aberrations

(File:Chromosome 21.png|thumb|In Down syndrome, there are three copies of chromosome 21)Chromosomal aberrations are disruptions in the normal chromosomal content of a cell and are a major cause of genetic conditions in humans, such as Down syndrome, although most aberrations have little to no effect. Some chromosome abnormalities do not cause disease in carriers, such as translocations, or chromosomal inversions, although they may lead to a higher chance of bearing a child with a chromosome disorder. Abnormal numbers of chromosomes or chromosome sets, called aneuploidy, may be lethal or may give rise to genetic disorders.JOURNAL, Santaguida S, Amon A, Short- and long-term effects of chromosome mis-segregation and aneuploidy, Nature Reviews. Molecular Cell Biology, 16, 8, 473–85, August 2015, 26204159, 10.1038/nrm4025, 1721.1/117201, Genetic counseling is offered for families that may carry a chromosome rearrangement.The gain or loss of DNA from chromosomes can lead to a variety of genetic disorders. Human examples include:
  • Cri du chat, which is caused by the deletion of part of the short arm of chromosome 5. "Cri du chat" means "cry of the cat" in French; the condition was so-named because affected babies make high-pitched cries that sound like those of a cat. Affected individuals have wide-set eyes, a small head and jaw, moderate to severe mental health problems, and are very short.
  • Down syndrome, the most common trisomy, usually caused by an extra copy of chromosome 21 (trisomy 21). Characteristics include decreased muscle tone, stockier build, asymmetrical skull, slanting eyes and mild to moderate developmental disability.BOOK, Miller, Kenneth R., vanc, Biology, Prentice Hall, Upper Saddle River, New Jersey, 2000, 5th, 194–5, Chapter 9-3, 978-0-13-436265-6,
  • Edwards syndrome, or trisomy-18, the second most common trisomy.WEB, What is Trisomy 18?,weblink Trisomy 18 Foundation, 4 February 2017, Symptoms include motor retardation, developmental disability and numerous congenital anomalies causing serious health problems. Ninety percent of those affected die in infancy. They have characteristic clenched hands and overlapping fingers.
  • Isodicentric 15, also called idic(15), partial tetrasomy 15q, or inverted duplication 15 (inv dup 15).
  • Jacobsen syndrome, which is very rare. It is also called the terminal 11q deletion disorder.European Chromosome 11 Network{{failed verification|date=November 2013}} Those affected have normal intelligence or mild developmental disability, with poor expressive language skills. Most have a bleeding disorder called Paris-Trousseau syndrome.
  • Klinefelter syndrome (XXY). Men with Klinefelter syndrome are usually sterile and tend to be taller and have longer arms and legs than their peers. Boys with the syndrome are often shy and quiet and have a higher incidence of speech delay and dyslexia. Without testosterone treatment, some may develop gynecomastia during puberty.
  • Patau Syndrome, also called D-Syndrome or trisomy-13. Symptoms are somewhat similar to those of trisomy-18, without the characteristic folded hand.
  • Small supernumerary marker chromosome. This means there is an extra, abnormal chromosome. Features depend on the origin of the extra genetic material. Cat-eye syndrome and isodicentric chromosome 15 syndrome (or Idic15) are both caused by a supernumerary marker chromosome, as is Pallister–Killian syndrome.
  • Triple-X syndrome (XXX). XXX girls tend to be tall and thin and have a higher incidence of dyslexia.
  • Turner syndrome (X instead of XX or XY). In Turner syndrome, female sexual characteristics are present but underdeveloped. Females with Turner syndrome often have a short stature, low hairline, abnormal eye features and bone development and a "caved-in" appearance to the chest.
  • Wolf–Hirschhorn syndrome, which is caused by partial deletion of the short arm of chromosome 4. It is characterized by growth retardation, delayed motor skills development, "Greek Helmet" facial features, and mild to profound mental health problems.
  • XYY syndrome. XYY boys are usually taller than their siblings. Like XXY boys and XXX girls, they are more likely to have learning difficulties.

Sperm aneuploidy

Exposure of males to certain lifestyle, environmental and/or occupational hazards may increase the risk of aneuploid spermatozoa.JOURNAL, Templado C, Uroz L, Estop A, New insights on the origin and relevance of aneuploidy in human spermatozoa, Molecular Human Reproduction, 19, 10, 634–43, October 2013, 23720770, 10.1093/molehr/gat039, In particular, risk of aneuploidy is increased by tobacco smoking,JOURNAL, Shi Q, Ko E, Barclay L, Hoang T, Rademaker A, Martin R, Cigarette smoking and aneuploidy in human sperm, Molecular Reproduction and Development, 59, 4, 417–21, August 2001, 11468778, 10.1002/mrd.1048, JOURNAL, Rubes J, Lowe X, Moore D, Perreault S, Slott V, Evenson D, Selevan SG, Wyrobek AJ, Smoking cigarettes is associated with increased sperm disomy in teenage men, Fertility and Sterility, 70, 4, 715–23, October 1998, 9797104, 10.1016/S0015-0282(98)00261-1, and occupational exposure to benzene,JOURNAL, Xing C, Marchetti F, Li G, Weldon RH, Kurtovich E, Young S, Schmid TE, Zhang L, Rappaport S, Waidyanatha S, Wyrobek AJ, Eskenazi B, Benzene exposure near the U.S. permissible limit is associated with sperm aneuploidy, Environmental Health Perspectives, 118, 6, 833–9, June 2010, 20418200, 2898861, 10.1289/ehp.0901531, insecticides,JOURNAL, Xia Y, Bian Q, Xu L, Cheng S, Song L, Liu J, Wu W, Wang S, Wang X, Genotoxic effects on human spermatozoa among pesticide factory workers exposed to fenvalerate, Toxicology, 203, 1–3, 49–60, October 2004, 15363581, 10.1016/j.tox.2004.05.018, JOURNAL, Xia Y, Cheng S, Bian Q, Xu L, Collins MD, Chang HC, Song L, Liu J, Wang S, Wang X, Genotoxic effects on spermatozoa of carbaryl-exposed workers, Toxicological Sciences, 85, 1, 615–23, May 2005, 15615886, 10.1093/toxsci/kfi066, and perfluorinated compounds.JOURNAL, Governini L, Guerranti C, De Leo V, Boschi L, Luddi A, Gori M, Orvieto R, Piomboni P, Chromosomal aneuploidies and DNA fragmentation of human spermatozoa from patients exposed to perfluorinated compounds, Andrologia, 47, 9, 1012–9, November 2015, 25382683, 10.1111/and.12371, Increased aneuploidy is often associated with increased DNA damage in spermatozoa.

See also

X-inactivation Y-chromosomal Aaron Y-chromosomal Adam

Notes and references

{{Reflist|32em}}

External links

{{commons category|Chromosomes}} {{Chromosome genetics}}{{Authority control}}

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