Chromosome 21 ( human ) - wikipedia Chromosome 21 ( human ) This article includes a list of references, but its sources remain unclear because it has insufficient inline citations. Please help to improve this article by introducing more precise citations. ( February 2013 ) Chromosome 21 ( human ) Human chromosome 21 pair after G - banding. One is from mother, one is from father. Chromosome 21 pair in human male karyogram. Features Length ( bp ) 46,709,983 bp ( GRCh38 ) No. of genes 215 ( CCDS ) Type Autosome Centromere position Acrocentric ( 12.0 Mbp ) Complete gene lists CCDS Gene list HGNC Gene list NCBI Gene list External map viewers Ensembl Chromosome 21 Entrez Chromosome 21 NCBI Chromosome 21 UCSC Chromosome 21 Full DNA sequences RefSeq NC_000021 ( FASTA ) GenBank CM000683 ( FASTA ) Chromosome 21 is one of the 23 pairs of chromosomes in humans. Chromosome 21 is the smallest human autosome, with 48 million nucleotides ( the building material of DNA ) representing about 1.5 percent of the total DNA in cells. Most people have two copies of chromosome 21, while those with three copies of chromosome 21 have Down syndrome, also called `` trisomy 21 ''. Researchers working on the Human Genome Project announced that they had determined the sequence of base pairs that make up this chromosome. Chromosome 21 was the second human chromosome to be fully sequenced, after chromosome 22. Contents 1 Genes 1.1 Number of genes 1.2 Gene list 2 Diseases and disorders 3 Chromosomal conditions 4 Cytogenetic band 5 References 6 External links Genes Number of genes The following are some of the gene count estimates of human chromosome 21. Because researchers use different approaches to genome annotation their predictions of the number of genes on each chromosome varies ( for technical details, see gene prediction ). Among various projects, the collaborative consensus coding sequence project ( CCDS ) takes an extremely conservative strategy. So CCDS 's gene number prediction represents a lower bound on the total number of human protein - coding genes. Estimated by Protein - coding genes Non-coding RNA genes Pseudogenes Source Release date CCDS 215 - - 2016 - 09 - 08 HGNC 217 165 180 2017 - 05 - 12 Ensembl 234 404 183 2017 - 03 - 29 NCBI 256 356 207 2017 - 05 - 19 Gene list See also : Category : Genes on human chromosome 21. The following is a partial list of genes on human chromosome 21. For complete list, see the link in the infobox on the right. ADAMTS1 APP : amyloid beta ( A4 ) precursor protein ( peptidase nexin - II, Alzheimer disease ) C21orf45 : encoding protein Protein Mis18 - alpha C21orf55 / DNAJC28 : encoding protein DnaJ homolog subfamily C member 28 C21orf56 : encoding protein Uncharacterized protein C21orf56 C21orf59 : Chromosome 21 open reading frame 59 C21orf62 : expressed in tissues of the brain and reproductive organs C21orf66 : encoding protein GC - rich sequence DNA - binding factor homolog CBS : cystathionine - beta - synthase CLDN14 : claudin 14 CRYZL1 : Crystallin zeta - like 1 CTSB CYYR1 : Cysteine and tyrosine rich 1 DIP2A : Disco - interacting protein 2 homolog A DOPEY2 : Dopey family member 2 DSCR1 : Down Syndrome critical region 1 DYRK1A : dual specificity tyrosine - ( Y ) - phosphorylation regulated kinase 1A ERG ETS2 FAM3B : Family with sequence similarity 3 member B FRGCA : encoding protein FOXM1 - regulated, gastric cancer associated HLCS : holocarboxylase synthetase ( biotin - ( propionyl - Coenzyme A-carboxylase ( ATP - hydrolysing ) ) ligase ) KCNE1 : potassium voltage - gated channel, Isk - related family, member 1 KCNE2 : potassium voltage - gated channel, Isk - related family, member 2 LAD : leukocyte adhesion deficiency ( symbols are ITGB2, CD18, LCAMB ) NRIP1 OLIG2 PCNT : centrosomal pericentrin PDXK : encoding enzyme Pyridoxal kinase PSMG1 : Proteasome assembly chaperone 1 RNR4 : RNA, ribosomal 45S cluster 4 RRP1 : encoding protein Ribosomal RNA processing protein 1 homolog A RRP1B : ribosomal RNA processing 1 homolog B RWDD2B : encoding protein RWD domain - containing protein 2B RUNX1 S100B : calcium binding protein SOD1 : superoxide dismutase 1, soluble ( amyotrophic lateral sclerosis 1 ( adult ) ) TFF1, TFF2, TFF3 TIAM1 TMEM1 : encoding protein Trafficking protein particle complex subunit 10 TMPRSS2 TMPRSS3 : transmembrane protease, serine 3 TTC3 : Tetratricopeptide Repeat Domain 3 Diseases and disorders The following diseases are some of those related to genes on chromosome 21 : Alzheimer 's disease Amyotrophic lateral sclerosis Autoimmune polyendocrine syndrome Down syndrome Erondu -- Cymet syndrome Holocarboxylase synthetase deficiency Homocystinuria Jervell and Lange - Nielsen syndrome Leukocyte adhesion deficiency Majewski osteodysplastic primordial dwarfism type II ( MOPD II, or MOPD2 ) Nonsyndromic deafness Romano -- Ward syndrome Chromosomal conditions Translocation Down 's syndrome affecting Chromosome 21 The following conditions are caused by changes in the structure or number of copies of chromosome 21 : Cancers : Rearrangements ( translocations ) of genetic material between chromosome 21 and other chromosomes have been associated with several types of cancer. For example, acute lymphoblastic leukemia ( a type of blood cancer most often diagnosed in childhood ) has been associated with a translocation between chromosomes 12 and 21. Another form of leukemia, acute myeloid leukemia, has been associated with a translocation between chromosomes 8 and 21. In a small percentage of cases, Down syndrome is caused by a rearrangement of chromosomal material between chromosome 21 and another chromosome. As a result, a person has the usual two copies of chromosome 21, plus extra material from chromosome 21 attached to another chromosome. These cases are called translocation Down syndrome. Researchers believe that extra copies of genes on chromosome 21 disrupt the course of normal development, causing the characteristic features of Down syndrome and the increased risk of medical problems associated with this disorder. Other changes in the number or structure of chromosome 21 can have a variety of effects, including intellectual disability, delayed development, and characteristic facial features. In some cases, the signs and symptoms are similar to those of Down syndrome. Changes to chromosome 21 include a missing segment of the chromosome in each cell ( partial monosomy 21 ) and a circular structure called ring chromosome 21. A ring chromosome occurs when both ends of a broken chromosome are reunited. Duplication in Amyloid precursor protein ( APP ) locus ( duplicated segment varies in length but includes APP ) on Chromosome 21 was found to cause early onset familial Alzheimer 's disease in a French family set ( Rovelet - Lecrux et al. ) and a Dutch family set. Compared to Alzheimer 's caused by missense mutations in APP, the frequency of the Alzheimer 's caused by APP duplications is significant. All patients that have an extra copy of APP gene due to the locus duplication show Alzheimer 's with severe cerebral amyloid angiopathy. Cytogenetic band G - banding ideograms of human chromosome 21 G - banding ideogram of human chromosome 21 in resolution 850 bphs. Band length in this diagram is proportional to base - pair length. This type of ideogram is generally used in genome browsers ( e.g. Ensembl, UCSC Genome Browser ). G - banding patterns of human chromosome 21 in three different resolutions ( 400, 550 and 850 ). Band length in this diagram is based on the ideograms from ISCN ( 2013 ). This type of ideogram represents actual relative band length observed under a microscope at the different moments during the mitotic process. G - bands of human chromosome 21 in resolution 850 bphs Chr. Arm Band ISCN start ISCN stop Basepair start Basepair stop Stain Density 21 p 13 0 311 7000100000000000000 ♠ 1 7006310000000000000 ♠ 3,100,000 gvar 21 p 12 311 683 7006310000100000000 ♠ 3,100,001 7006700000000000000 ♠ 7,000,000 stalk 21 p 11.2 683 1056 7006700000100000000 ♠ 7,000,001 7007109000000000000 ♠ 10,900,000 gvar 21 p 11.1 1056 1274 7007109000010000000 ♠ 10,900,001 7007120000000000000 ♠ 12,000,000 acen 21 q 11.1 1274 1367 7007120000010000000 ♠ 12,000,001 7007130000000000000 ♠ 13,000,000 acen 21 q 11.2 1367 1584 7007130000010000000 ♠ 13,000,001 7007150000000000000 ♠ 15,000,000 gneg 21 q 21.1 1584 2019 7007150000010000000 ♠ 15,000,001 7007226000000000000 ♠ 22,600,000 gpos 100 21 q 21.2 2019 2144 7007226000010000000 ♠ 22,600,001 7007255000000000000 ♠ 25,500,000 gneg 21 q 21.3 2144 2330 7007255000010000000 ♠ 25,500,001 7007302000000000000 ♠ 30,200,000 gpos 75 21 q 22.11 2330 2485 7007302000010000000 ♠ 30,200,001 7007344000000000000 ♠ 34,400,000 gneg 21 q 22.12 2485 2610 7007344000010000000 ♠ 34,400,001 7007364000000000000 ♠ 36,400,000 gpos 50 21 q 22.13 2610 2703 7007364000010000000 ♠ 36,400,001 7007383000000000000 ♠ 38,300,000 gneg 21 q 22.2 2703 2858 7007383000010000000 ♠ 38,300,001 7007412000000000000 ♠ 41,200,000 gpos 50 21 q 22.3 2858 3200 7007412000010000000 ♠ 41,200,001 7007467099830000000 ♠ 46,709,983 gneg References Jump up ^ `` Human Genome Assembly GRCh38 - Genome Reference Consortium ''. National Center for Biotechnology Information. 2013 - 12 - 24. Retrieved 2017 - 03 - 04. ^ Jump up to : `` Search results - 21 ( CHR ) AND `` Homo sapiens '' ( Organism ) AND ( `` has ccds '' ( Properties ) AND alive ( prop ) ) - Gene ``. NCBI. CCDS Release 20 for Homo sapiens. 2016 - 09 - 08. Retrieved 2017 - 05 - 28. Jump up ^ Tom Strachan ; Andrew Read ( 2 April 2010 ). Human Molecular Genetics. Garland Science. p. 45. ISBN 978 - 1 - 136 - 84407 - 2. ^ Jump up to : Genome Decoration Page, NCBI. Ideogram data for Homo sapience ( 850 bphs, Assembly GRCh38. p3 ). Last update 2014 - 06 - 03. Retrieved 2017 - 04 - 26. Jump up ^ Pertea M, Salzberg SL ( 2010 ). `` Between a chicken and a grape : estimating the number of human genes ''. Genome Biol. 11 ( 5 ) : 206. doi : 10.1186 / gb - 2010 - 11 - 5 - 206. PMC 2898077. PMID 20441615. Jump up ^ `` Statistics & Downloads for chromosome 21 ''. HUGO Gene Nomenclature Committee. 2017 - 05 - 12. Retrieved 2017 - 05 - 19. Jump up ^ `` Chromosome 21 : Chromosome summary - Homo sapiens ''. Ensembl Release 88. 2017 - 03 - 29. Retrieved 2017 - 05 - 19. Jump up ^ `` Search results - 21 ( CHR ) AND `` Homo sapiens '' ( Organism ) AND ( `` genetype protein coding '' ( Properties ) AND alive ( prop ) ) - Gene ``. NCBI. 2017 - 05 - 19. Retrieved 2017 - 05 - 20. Jump up ^ `` Search results - 21 ( CHR ) AND `` Homo sapiens '' ( Organism ) AND ( ( `` genetype miscrna '' ( Properties ) OR `` genetype ncrna '' ( Properties ) OR `` genetype rrna '' ( Properties ) OR `` genetype trna '' ( Properties ) OR `` genetype scrna '' ( Properties ) OR `` genetype snrna '' ( Properties ) OR `` genetype snorna '' ( Properties ) ) NOT `` genetype protein coding '' ( Properties ) AND alive ( prop ) ) - Gene ``. NCBI. 2017 - 05 - 19. Retrieved 2017 - 05 - 20. Jump up ^ `` Search results - 21 ( CHR ) AND `` Homo sapiens '' ( Organism ) AND ( `` genetype pseudo '' ( Properties ) AND alive ( prop ) ) - Gene ``. NCBI. 2017 - 05 - 19. Retrieved 2017 - 05 - 20. ^ Jump up to : Sleegers K, Brouwers N, Gijselinck I, Theuns J, Goossens D, Wauters J, Del - Favero J, Cruts M, van Duijn CM, Van Broeckhoven C ( 2006 ). `` APP duplication is sufficient to cause early onset Alzheimer 's dementia with cerebral amyloid angiopathy ''. Brain. 129 ( Pt 11 ) : 2977 -- 83. doi : 10.1093 / brain / awl203. PMID 16921174. Jump up ^ Gardiner K, Davisson M ( 2000 ). `` The sequence of human chromosome 21 and implications for research into Down syndrome ''. Genome Biol. 1 ( 2 ) : REVIEWS0002. doi : 10.1186 / gb - 2000 - 1 - 2 - reviews0002. PMC 138845. PMID 11178230. Jump up ^ Genome Decoration Page, NCBI. Ideogram data for Homo sapience ( 400 bphs, Assembly GRCh38. p3 ). Last update 2014 - 03 - 04. Retrieved 2017 - 04 - 26. Jump up ^ Genome Decoration Page, NCBI. Ideogram data for Homo sapience ( 550 bphs, Assembly GRCh38. p3 ). Last update 2015 - 08 - 11. Retrieved 2017 - 04 - 26. Jump up ^ International Standing Committee on Human Cytogenetic Nomenclature ( 2013 ). ISCN 2013 : An International System for Human Cytogenetic Nomenclature ( 2013 ). Karger Medical and Scientific Publishers. ISBN 978 - 3 - 318 - 02253 - 7. Jump up ^ Sethakulvichai, W. ; Manitpornsut, S. ; Wiboonrat, M. ; Lilakiatsakun, W. ; Assawamakin, A. ; Tongsima, S. ( 2012 ). `` Estimation of band level resolutions of human chromosome images '' ( PDF ). In Computer Science and Software Engineering ( JCSSE ), 2012 International Joint Conference on : 276 -- 282. doi : 10.1109 / JCSSE. 2012.6261965. ISBN 978 - 1 - 4673 - 1921 - 8. Jump up ^ Genome Decoration Page, NCBI. Ideogram data for Homo sapience ( 850 bphs, Assembly GRCh38. p3 ). Last update 2014 - 06 - 03. Retrieved 2017 - 04 - 26. Jump up ^ `` p '' : Short arm ; `` q '' : Long arm. Jump up ^ For cytogenetic banding nomenclature, see article locus. ^ Jump up to : These values ( ISCN start / stop ) are based on the length of bands / ideograms from the ISCN book, An International System for Human Cytogenetic Nomenclature ( 2013 ). Arbitrary unit. Jump up ^ gpos : Region which is positively stained by G banding, generally AT - rich and gene poor ; gneg : Region which is negatively stained by G banding, generally CG - rich and gene rich ; acen Centromere. var : Variable region ; stalk : Stalk. Antonarakis SE, Lyle R, Dermitzakis ET, Reymond A, Deutsch S ( 2004 ). `` Chromosome 21 and down syndrome : from genomics to pathophysiology ''. Nat Rev Genet. 5 ( 10 ) : 725 -- 38. doi : 10.1038 / nrg1448. PMID 15510164. Antonarakis SE, Lyle R, Deutsch S, Reymond A ( 2002 ). `` Chromosome 21 : a small land of fascinating disorders with unknown pathophysiology ''. Int J Dev Biol. 46 ( 1 ) : 89 -- 96. PMID 11902692. Antonarakis SE ( 2001 ). `` Chromosome 21 : from sequence to applications ''. Curr Opin Genet Dev. 11 ( 3 ) : 241 -- 6. doi : 10.1016 / S0959 - 437X ( 00 ) 00185 - 4. PMID 11377958. Gilbert F ( 1997 ). `` Disease genes and chromosomes : disease maps of the human genome. Chromosome 21 ''. Genet Test. 1 ( 4 ) : 301 -- 6. doi : 10.1089 / gte. 1997.1. 301. PMID 10464663. Hattori M, Fujiyama A, Taylor TD, Watanabe H, Yada T, Park HS, Toyoda A, Ishii K, Totoki Y, Choi DK, Groner Y, Soeda E, Ohki M, Takagi T, Sakaki Y, Taudien S, Blechschmidt K, Polley A, Menzel U, Delabar J, Kumpf K, Lehmann R, Patterson D, Reichwald K, Rump A, Schillhabel M, Schudy A, Zimmermann W, Rosenthal A, Kudoh J, Schibuya K, Kawasaki K, Asakawa S, Shintani A, Sasaki T, Nagamine K, Mitsuyama S, Antonarakis SE, Minoshima S, Shimizu N, Nordsiek G, Hornischer K, Brant P, Scharfe M, Schon O, Desario A, Reichelt J, Kauer G, Blocker H, Ramser J, Beck A, Klages S, Hennig S, Riesselmann L, Dagand E, Haaf T, Wehrmeyer S, Borzym K, Gardiner K, Nizetic D, Francis F, Lehrach H, Reinhardt R, Yaspo ML ( 2000 ). `` The DNA sequence of human chromosome 21 ''. Nature. 405 ( 6784 ) : 311 -- 9. doi : 10.1038 / 35012518. PMID 10830953. Sawinska M, Ladon D ( 2004 ). `` Mechanism, detection and clinical significance of the reciprocal translocation t ( 12 ; 21 ) ( p12 ; q22 ) in the children suffering from acute lymphoblastic leukaemia ''. Leuk Res. 28 ( 1 ) : 35 -- 42. doi : 10.1016 / S0145 - 2126 ( 03 ) 00160 - 7. PMID 14630078. Rovelet - Lecrux A, Hannequin D, Raux G, Le Meur N, Laquerriere A, Vital A, Dumanchin C, Feuillette S, Brice A, Vercelletto M, Dubas F, Frebourg T, Campion D ( 2005 ). `` APP locus duplication causes autosomal dominant early - onset Alzheimer disease with cerebral amyloid angiopathy ''. Nature Genetics. 38 ( 1 ) : 24 -- 6. doi : 10.1038 / ng1718. PMID 16369530. Anita Rauch ; Christian T. Thiel ; Detlev Schindler ; Ursula Wick ; Yanick J. Crow ; Arif B. Ekici ; Anthonie J. van Essen ; Timm O. Goecke ; Lihadh Al - Gazali ; Krystyna H. Chrzanowska ; Christiane Zweier ; Han G. Brunner ; Kristin Becker ; Cynthia J. Curry ; Bruno Dallapiccola ; Koenraad Devriendt ; Arnd Dörfler ; Esther Kinning ; André Megarbane ; Peter Meinecke ; Robert K. Semple ; Stephanie Spranger ; Annick Toutain ; Richard C. Trembath ; Egbert Voss ; Louise Wilson ; Raoul Hennekam ; Francis de Zegher ; Helmut - Günther Dörr ; André Reis ( 2008 ). `` Mutations in the Pericentrin ( PCNT ) Gene Cause Primordial Dwarfism ''. Science Online : 7. External links Wikimedia Commons has media related to Human chromosome 21. National Institutes of Health. `` Chromosome 21 ''. Genetics Home Reference. Retrieved 2017 - 05 - 06. `` Chromosome 21 ''. Human Genome Project Information Archive 1990 -- 2003. Retrieved 2017 - 05 - 06. Human genome Nuclear genome Autosome 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 Sex chromosome X Y Mitochondrial genome Human mitochondrial DNA Cytogenetics : chromosomes Basic concepts Karyotype Ploidy Genetic material / Genome Chromatin Euchromatin Heterochromatin Chromosome Chromatid Nucleosome Nuclear organization Types Autosome / Sex chromosome ( or allosome or heterosome ) Macrochromosome / Microchromosome Circular chromosome / Linear chromosome Extra chromosome ( or accessory chromosome ) Supernumerary chromosome A chromosome / B chromosome Lampbrush chromosome Polytene chromosome Dinoflagellate chromosomes Homologous chromosome Isochromosome Satellite chromosome Centromere position Metacentric Submetacentric Telocentric Acrocentric Holocentric Centromere number Acentric Monocentric Dicentric Polycentric Processes and evolution Mitosis Meiosis Structural alterations Chromosomal inversion Chromosomal translocation Numerical alterations Aneuploidy Euploidy Polyploidy Paleopolyploidy Polyploidization Structures Telomere : Telomere - binding protein ( TINF2 ) Protamine Histone H1 H2A H2B H3 H4 Centromere C1 C2 Q See also Extrachromosomal DNA Plasmid List of organisms by chromosome count List of chromosome lengths for various organisms List of sequenced genomes International System for Human Cytogenetic Nomenclature Retrieved from `` https://en.wikipedia.org/w/index.php?title=Chromosome_21_(human)&oldid=821761164 '' Categories : Chromosomes ( human ) Genes on human chromosome 21 Hidden categories : Articles lacking in - text citations from February 2013 All articles lacking in - text citations Pages using div col without cols and colwidth parameters Talk Contents About Wikipedia বাংলা Bân - lâm - gú Bosanski Català Deutsch Eesti Español فارسی Français Galego Hrvatski Italiano Magyar Nederlands 日本 語 Norsk Polski Português Română Русский Српски / srpski Srpskohrvatski / српскохрватски Tagalog Türkçe Українська Tiếng Việt 中文 Edit links This page was last edited on 22 January 2018, at 13 : 42. About Wikipedia

Question: where does the extra chromosome 21 come from
Answer: a rearrangement of chromosomal material between chromosome 21 and another chromosome