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X chromosome
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Human X chromosome
Human X chromosome (after G-banding).
X chromosome in human male karyogram.
Features
Length (bp)
156,040,895 bp
(GRCh38)[1]
No. of genes
804 (CCDS)[2]
Type
Allosome
Centromere position
Submetacentric[3]
(61.0 Mbp[4])
External map viewers
Ensembl
Chromosome X
Entrez
Chromosome X
NCBI
Chromosome X
UCSC
Chromosome X
Full DNA sequences
RefSeq
NC_000023 (FASTA)
GenBank
CM000685 (FASTA)
The X chromosome is one of the two sex-determining chromosomes (allosomes) in many organisms, including mammals (the other is the Y chromosome), and is found in both males and females. It is a part of the XY sex-determination system and X0 sex-determination system. The X chromosome was named for its unique properties by early researchers, which resulted in the naming of its counterpart Y chromosome, for the next letter in the alphabet, after it was discovered later.[5]
Contents
[hide]
1 Discovery
2 Inheritance pattern
3 Humans
3.1 Function
3.2 Genes
3.3 Structure
3.4 Role in diseases
3.4.1 Numerical abnormalities
3.4.2 Other disorders
3.4.3 Role in mental abilities and intelligence
3.5 Cytogenetic band
4 See also
5 References
6 External links
Discovery[edit]
It was first noted that the X chromosome was special in 1890 by Hermann Henking in Leipzig. Henking was studying the testicles of Pyrrhocoris and noticed that one chromosome did not take part in meiosis. Chromosomes are so named because of their ability to take up staining. Although the X chromosome could be stained just as well as the others, Henking was unsure whether it was a different class of object and consequently named it X element,[6] which later became X chromosome after it was established that it was indeed a chromosome.[7]
The idea that the X chromosome was named after its similarity to the letter "X" is mistaken. All chromosomes normally appear as an amorphous blob under the microscope and only take on a well defined shape during mitosis. This shape is vaguely X-shaped for all chromosomes. It is entirely coincidental that the Y chromosome, during mitosis, has two very short branches which can look merged under the microscope and appear as the descender of a Y-shape.[8]
It was first suggested that the X chromosome was involved in sex determination by Clarence Erwin McClung in 1901 after comparing his work on locusts with Henking's and others. McClung noted that only half the sperm received an X chromosome. He called this chromosome an accessory chromosome and insisted, correctly, that it was a proper chromosome, and theorized, incorrectly, that it was the male determining chromosome.[6]
Inheritance pattern[edit]
The number of possible ancestors on the X chromosome inheritance line at a given ancestral generation follows the Fibonacci sequence. (After Hutchison, L. "Growing the Family Tree: The Power of DNA in Reconstructing Family Relationships".[9])
Luke Hutchison noticed that a number of possible ancestors on the X chromosome inheritance line at a given ancestral generation follows the Fibonacci sequence.[9] A male individual has an X chromosome, which he received from his mother, and a Y chromosome, which he received from his father. The male counts as the "origin" of his own X chromosome ( F 1 = 1 {\displaystyle F_{1}=1} ), and at his parents' generation, his X chromosome came from a single parent ( F 2 = 1 {\displaystyle F_{2}=1} ). The male's mother received one X chromosome from her mother (the son's maternal grandmother), and one from her father (the son's maternal grandfather), so two grandparents contributed to the male descendant's X chromosome ( F 3 = 2 {\displaystyle F_{3}=2} ). The maternal grandfather received his X chromosome from his mother, and the maternal grandmother received X chromosomes from both of her parents, so three great-grandparents contributed to the male descendant's X chromosome ( F 4 = 3 {\displaystyle F_{4}=3} ). Five great-great-grandparents contributed to the male descendant's X chromosome ( F 5 = 5 {\displaystyle F_{5}=5} ), etc. (Note that this assumes that all ancestors of a given descendant are independent, but if any genealogy is traced far enough back in time, ancestors begin to appear on multiple lines of the genealogy, until eventually, a population founder appears on all lines of the genealogy.)
Humans[edit]
Function[edit]
Nucleus of a female amniotic fluid cell. Top: Both X-chromosome territories are detected by FISH. Shown is a single optical section made with a confocal microscope. Bottom: Same nucleus stained with DAPI and recorded with a CCD camera. The Barr body is indicated by the arrow, it identifies the inactive X (Xi).
The X chromosome in humans spans more than 153 million base pairs (the building material of DNA). It represents about 800 protein-coding genes compared to the Y chromosome containing about 70 genes, out of 20,000 - 25,000 total genes in the human genome. Each person usually has one pair of sex chromosomes in each cell. Females have two X chromosomes, whereas males have one X and one Y chromosome. Both males and females retain one of their mother's X chromosomes, and females retain their second X chromosome from their father. Since the father retains his X chromosome from his mother, a human female has one X chromosome from her paternal grandmother (father's side), and one X chromosome from her mother. This inheritance pattern follows the Fibonacci numbers at a given ancestral depth.
Genetic disorders that are due to mutations in genes on the X chromosome are described as X linked.
The X chromosome carries hundreds of genes but few, if any, of these have anything to do directly with sex determination. Early in embryonic development in females, one of the two X chromosomes is randomly and permanently inactivated in nearly all somatic cells (cells other than egg and sperm cells). This phenomenon is called X-inactivation or Lyonization, and creates a Barr body. If X-inactivation in the somatic cell meant a complete de-functionalizing of one of the X-chromosomes, it would ensure that females, like males, had only one functional copy of the X chromosome in each somatic cell. This was previously assumed to be the case. However, recent research suggests that the Barr body may be more biologically active than was previously supposed.[10]
Genes[edit]
See also: Category:Genes on human chromosome X.
The following are some of the gene count estimates of human X chromosome. 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.[11]
Estimated by Protein-coding genes Non-coding RNA genes Pseudogenes Source Release date
CCDS 804 - - [2] 2016-09-08
HGNC 825 260 606 [12] 2017-05-12
Ensembl 841 639 871 [13] 2017-03-29
NCBI 874 494 879 [14][15][16] 2017-05-19
The following are some of the genes located on chromosome X:
APOO: encoding protein Apolipoprotein O
ARMCX6: encoding protein Armadillo repeat containing X-linked 6
BEX1: encoding protein Brain-expressed X-linked protein 1
BEX2: encoding protein Brain-expressed X-linked protein 2
BEX4: encoding protein Brain expressed, X-linked 4
CCDC120: encoding protein Coiled coil domain containing protein 120
CCDC22: encoding protein Coiled-coil domain containing 22
CD99L2: CD99 antigen-like protein 2
CHRDL1: encoding protein Chordin-like 1
CMTX2 encoding protein Charcot-Marie-Tooth neuropathy, X-linked 2 (recessive)
CMTX3 encoding protein Charcot-Marie-Tooth neuropathy, X-linked 3 (dominant)
CT45A5: encoding protein Cancer/testis antigen family 45, member A5
CXorf36: encoding protein hypothetical protein LOC79742
CXorf40A: Chromosome X open reading frame 40
CXorf49: chromosome X open reading frame 49. encoding protein
CXorf66: encoding protein Chromosome X Open Reading Frame 66
CXorf67: encoding protein Uncharacterized protein CXorf67
DACH2: encoding protein Dachshund homolog 2
EFHC2: encoding protein EF-hand domain (C-terminal) containing 2
ERCC6L encoding protein ERCC excision repair 6 like, spindle assembly checkpoint helicase
F8A1: Factor VIII intron 22 protein
FAM120C: encoding protein Family with sequence similarity 120C
FAM122B: Family with sequence similarity 122 member B
FAM122C: encoding protein Family with sequence similarity 122C
FAM127A: CAAX box protein 1
FAM50A: Family with sequence similarity 50 member A
FATE1: Fetal and adult testis-expressed transcript protein
FMR1-AS1: encoding a long non-coding RNA FMR1 antisense RNA 1
FRMPD3: encoding protein FERM and PDZ domain containing 3
FUNDC1: encoding protein FUN14 domain containing 1
FUNDC2: FUN14 domain-containing protein 2
GNL3L encoding protein G protein nucleolar 3 like
GPRASP2: G-protein coupled receptor-associated sorting protein 2
GRIPAP1: encoding protein GRIP1-associated protein 1
HDHD1A: encoding enzyme Haloacid dehalogenase-like hydrolase domain-containing protein 1A
LAS1L encoding protein LAS1-like protein
MAGEA2: encoding protein Melanoma-associated antigen 2
MAGEA5 encoding protein Melanoma antigen family A, 5
MAGEA8: encoding protein Melanoma antigen family A, 8
MAGED4B: encoding protein Melanoma-associated antigen D4
MAGT1: encoding protein Magnesium transporter protein 1
MBNL3: encoding protein Muscleblind-like protein 3
MIR222: encoding microRNA MicroRNA 222
MIR361: encoding microRNA MicroRNA 361
MIR660: encoding protein MicroRNA 660
MORF4L2: encoding protein Mortality factor 4-like protein 2
MOSPD1: encoding protein Motile sperm domain containing 1
MOSPD2: encoding protein Motile sperm domain containing 2
NKRF: encoding protein NF-kappa-B-repressing factor
NRK: encoding enzyme Nik-related protein kinase
OTUD5: encoding protein OTU deubiquitinase 5
PASD1: encoding protein PAS domain-containing protein 1
PBDC1: encoding [[]] FALSE
PCYT1B: encoding enzyme Choline-phosphate cytidylyltransferase B
PIN4: encoding enzyme Peptidyl-prolyl cis-trans isomerase NIMA-interacting 4
PLAC1: encoding protein Placenta-specific protein 1
PLP2: encoding protein Proteolipid protein 2
RPA4: encoding protein Replication protein A 30 kDa subunit
RPS6KA6: encoding protein Ribosomal protein S6 kinase, 90kDa, polypeptide 6
RRAGB: encoding protein Ras-related GTP-binding protein B
SFRS17A: encoding protein Splicing factor, arginine/serine-rich 17A
SLITRK2: encoding protein SLIT and NTRK-like protein 2
SMARCA1: encoding protein Probable global transcription activator SNF2L1
SMS: encoding enzyme Spermine synthase
SSR4: encoding protein Translocon-associated protein subunit delta
TAF7l: encoding protein TATA-box binding protein associated factor 7-like
TCEAL1: encoding protein Transcription elongation factor A protein-like 1
TCEAL4: encoding protein Transcription elongation factor A protein-like 4
THOC2: encoding protein THO complex subunit 2
TMEM29: encoding protein Protein FAM156A
TMEM47: encoding protein Transmembrane protein 47
TMLHE: encoding enzyme Trimethyllysine dioxygenase, mitochondrial
TNMD encoding protein Tenomodulin (also referred to as tendin, myodulin, Tnmd and TeM)
TRAPPC2P1 encoding protein Trafficking protein particle complex subunit 2
TREX2: encoding enzyme Three prime repair exonuclease 2
TRO: encoding protein Trophinin
TSPYL2: encoding protein Testis-specific Y-encoded-like protein 2
USP51: encoding enzyme Ubiquitin carboxyl-terminal hydrolase 51
YIPF6: encoding protein Protein YIPF6
ZC3H12B: encoding protein ZC3H12B
ZFP92: encoding protein ZFP92 zinc finger protein
ZMYM3: encoding protein Zinc finger MYM-type protein 3
ZNF157: encoding protein Zinc finger protein 157
ZNF182 encoding protein Zinc finger protein 182
ZNF275: encoding protein Zinc finger protein 275
ZNF674: encoding protein Zinc finger protein 674
Structure[edit]
It is theorized by Ross et al. 2005 and Ohno 1967 that the X chromosome is at least partially derived from the autosomal (non-sex-related) genome of other mammals, evidenced from interspecies genomic sequence alignments.
The X chromosome is notably larger and has a more active euchromatin region than its Y chromosome counterpart. Further comparison of the X and Y reveal regions of homology between the two. However, the corresponding region in the Y appears far shorter and lacks regions that are conserved in the X throughout primate species, implying a genetic degeneration for Y in that region. Because males have only one X chromosome, they are more likely to have an X chromosome-related disease.
It is estimated that about 10% of the genes encoded by the X chromosome are associated with a family of "CT" genes, so named because they encode for markers found in both tumor cells (in cancer patients) as well as in the human testis (in healthy patients).[17]
Role in diseases[edit]
Numerical abnormalities[edit]
Klinefelter syndrome:
Klinefelter syndrome is caused by the presence of one or more extra copies of the X chromosome in a male's cells. Extra genetic material from the X chromosome interferes with male sexual development, preventing the testicles from functioning normally and reducing the levels of testosterone.
Males with Klinefelter syndrome typically have one extra copy of the X chromosome in each cell, for a total of two X chromosomes and one Y chromosome (47,XXY). It is less common for affected males to have two or three extra X chromosomes (48,XXXY or 49,XXXXY) or extra copies of both the X and Y chromosomes (48,XXYY) in each cell. The extra genetic material may lead to tall stature, learning and reading disabilities, and other medical problems. Each extra X chromosome lowers the child's IQ by about 15 points,[18][19] which means that the average IQ in Klinefelter syndrome is in general in the normal range, although below average. When additional X and/or Y chromosomes are present in 48,XXXY, 48,XXYY, or 49,XXXXY, developmental delays and cognitive difficulties can be more severe and mild intellectual disability may be present.
Klinefelter syndrome can also result from an extra X chromosome in only some of the body's cells. These cases are called mosaic 46,XY/47,XXY.
Triple X syndrome (also called 47,XXX or trisomy X):
This syndrome results from an extra copy of the X chromosome in each of a female's cells. Females with trisomy X have three X chromosomes, for a total of 47 chromosomes per cell. The average IQ of females with this syndrome is 90, while the average IQ of unaffected siblings is 100.[20] Their stature on average is taller than normal females. They are fertile and their children do not inherit the condition.[21]
Females with more than one extra copy of the X chromosome (48, XXXX syndrome or 49, XXXXX syndrome) have been identified, but these conditions are rare.
Turner syndrome:
This results when each of a female's cells has one normal X chromosome and the other sex chromosome is missing or altered. The missing genetic material affects development and causes the features of the condition, including short stature and infertility.
About half of individuals with Turner syndrome have monosomy X (45,X), which means each cell in a woman's body has only one copy of the X chromosome instead of the usual two copies. Turner syndrome can also occur if one of the sex chromosomes is partially missing or rearranged rather than completely missing. Some women with Turner syndrome have a chromosomal change in only some of their cells. These cases are called Turner syndrome mosaics (45,X/46,XX).
Other disorders[edit]
Further information: X-linked recessive and X-linked dominant
XX male syndrome is a rare disorder, where the SRY region of the Y chromosome has recombined to be located on one of the X chromosomes. As a result, the XX combination after fertilization has the same effect as a XY combination, resulting in a male. However, the other genes of the X chromosome cause feminization as well.
X-linked endothelial corneal dystrophy is an extremely rare disease of cornea associated with Xq25 region. Lisch epithelial corneal dystrophy is associated with Xp22.3.
Megalocornea 1 is associated with Xq21.3-q22[medical citation needed]
Adrenoleukodystrophy, a rare and fatal disorder that is carried by the mother on the x-cell. It affects only boys between the ages of 5 and 10 and destroys the protective cell surrounding the nerves, myelin, in the brain. The female carrier hardly shows any symptoms because females have a copy of the x-cell. This disorder causes a once healthy boy to lose all abilities to walk, talk, see, hear, and even swallow. Within 2 years after diagnosis, most boys with Adrenoleukodystrophy die.
Role in mental abilities and intelligence[edit]
The X-chromosome has played a crucial role in the development of sexually selected characteristics for over 300 million years. During that time it has accumulated a disproportionate number of genes concerned with mental functions. For reasons that are not yet understood, there is an excess proportion of genes on the X-chromosome that are associated with the development of intelligence, with no obvious links to other significant biological functions.[22][23] .In other words, a significant proportion of genes associated with intelligence are passed on to the male offspring from the maternal side and to the female offspring from either/both maternal and paternal side.There has also been interest in the possibility that haploinsufficiency for one or more X-linked genes has a specific impact on development of the Amygdala and its connections with cortical centres involved in social–cognition processing or the ‘social brain'.[22][24][clarification needed]
Cytogenetic band[edit]
G-banding ideograms of human X chromosome
G-banding ideogram of human X chromosome 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 X chromosome in three different resolutions (400,[25] 550[26] and 850[4]). Band length in this diagram is based on the ideograms from ISCN (2013).[27] This type of ideogram represents actual relative band length observed under a microscope at the different moments during the mitotic process.[28]
G-bands of human X chromosome in resolution 850 bphs[4]
Chr.
Arm[29]
Band[30]
ISCN
start[31]
ISCN
stop[31]
Basepair
start
Basepair
stop
Stain[32]
Density
X p 22.33 0 323 7000100000000000000♠1 7006440000000000000♠4,400,000 gneg
X p 22.32 323 504 7006440000100000000♠4,400,001 7006610000000000000♠6,100,000 gpos 50
X p 22.31 504 866 7006610000100000000♠6,100,001 7006960000000000000♠9,600,000 gneg
X p 22.2 866 1034 7006960000100000000♠9,600,001 7007174000000000000♠17,400,000 gpos 50
X p 22.13 1034 1345 7007174000010000000♠17,400,001 7007192000000000000♠19,200,000 gneg
X p 22.12 1345 1448 7007192000010000000♠19,200,001 7007219000000000000♠21,900,000 gpos 50
X p 22.11 1448 1577 7007219000010000000♠21,900,001 7007249000000000000♠24,900,000 gneg
X p 21.3 1577 1784 7007249000010000000♠24,900,001 7007293000000000000♠29,300,000 gpos 100
X p 21.2 1784 1862 7007293000010000000♠29,300,001 7007315000000000000♠31,500,000 gneg
X p 21.1 1862 2120 7007315000010000000♠31,500,001 7007378000000000000♠37,800,000 gpos 100
X p 11.4 2120 2430 7007378000010000000♠37,800,001 7007425000000000000♠42,500,000 gneg
X p 11.3 2430 2624 7007425000010000000♠42,500,001 7007476000000000000♠47,600,000 gpos 75
X p 11.23 2624 2948 7007476000010000000♠47,600,001 7007501000000000000♠50,100,000 gneg
X p 11.22 2948 3129 7007501000010000000♠50,100,001 7007548000000000000♠54,800,000 gpos 25
X p 11.21 3129 3206 7007548000010000000♠54,800,001 7007581000000000000♠58,100,000 gneg
X p 11.1 3206 3297 7007581000010000000♠58,100,001 7007610000000000000♠61,000,000 acen
X q 11.1 3297 3491 7007610000010000000♠61,000,001 7007638000000000000♠63,800,000 acen
X q 11.2 3491 3620 7007638000010000000♠63,800,001 7007654000000000000♠65,400,000 gneg
X q 12 3620 3827 7007654000010000000♠65,400,001 7007685000000000000♠68,500,000 gpos 50
X q 13.1 3827 4137 7007685000010000000♠68,500,001 7007730000000000000♠73,000,000 gneg
X q 13.2 4137 4292 7007730000010000000♠73,000,001 7007747000000000000♠74,700,000 gpos 50
X q 13.3 4292 4447 7007747000010000000♠74,700,001 7007768000000000000♠76,800,000 gneg
X q 21.1 4447 4732 7007768000010000000♠76,800,001 7007854000000000000♠85,400,000 gpos 100
X q 21.2 4732 4809 7007854000010000000♠85,400,001 7007870000000000000♠87,000,000 gneg
X q 21.31 4809 5107 7007870000010000000♠87,000,001 7007927000000000000♠92,700,000 gpos 100
X q 21.32 5107 5184 7007927000010000000♠92,700,001 7007943000000000000♠94,300,000 gneg
X q 21.33 5184 5430 7007943000010000000♠94,300,001 7007991000000000000♠99,100,000 gpos 75
X q 22.1 5430 5701 7007991000010000000♠99,100,001 7008103300000000000♠103,300,000 gneg
X q 22.2 5701 5843 7008103300001000000♠103,300,001 7008104500000000000♠104,500,000 gpos 50
X q 22.3 5843 6050 7008104500001000000♠104,500,001 7008109400000000000♠109,400,000 gneg
X q 23 6050 6322 7008109400001000000♠109,400,001 7008117400000000000♠117,400,000 gpos 75
X q 24 6322 6619 7008117400001000000♠117,400,001 7008121800000000000♠121,800,000 gneg
X q 25 6619 7059 7008121800001000000♠121,800,001 7008129500000000000♠129,500,000 gpos 100
X q 26.1 7059 7253 7008129500001000000♠129,500,001 7008131300000000000♠131,300,000 gneg
X q 26.2 7253 7395 7008131300001000000♠131,300,001 7008134500000000000♠134,500,000 gpos 25
X q 26.3 7395 7602 7008134500001000000♠134,500,001 7008138900000000000♠138,900,000 gneg
X q 27.1 7602 7808 7008138900001000000♠138,900,001 7008141200000000000♠141,200,000 gpos 75
X q 27.2 7808 7886 7008141200001000000♠141,200,001 7008143000000000000♠143,000,000 gneg
X q 27.3 7886 8145 7008143000001000000♠143,000,001 7008148000000000000♠148,000,000 gpos 100
X q 28 8145 8610 7008148000001000000♠148,000,001 7008156040895000000♠156,040,895 gneg
See also[edit]
List of X-STR markers
Sex linkage
X-inactivation
Pseudoautosomal region
Y chromosome
References[edit]
Earlier versions of this article contain material from the National Library of Medicine (https://web.archive.org/web/20081122151614/http://www.nlm.nih.gov/copyright.html), a part of the National Institutes of Health (USA,) which, as a US government publication, is in the public domain.
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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: a b c 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 ^ Angier, Natalie (2007-05-01). "For Motherly X Chromosome, Gender Is Only the Beginning". New York Times. Retrieved 2007-05-01.
^ Jump up to: a b James Schwartz, In Pursuit of the Gene: From Darwin to DNA, pages 155-158, Harvard University Press, 2009 ISBN 0674034910
Jump up ^ David Bainbridge, 'The X in Sex: How the X Chromosome Controls Our Lives, pages 3-5, Harvard University Press, 2003 ISBN 0674016211.
Jump up ^ Bainbridge, pages 65-66
^ Jump up to: a b Hutchison, Luke (September 2004). "Growing the Family Tree: The Power of DNA in Reconstructing Family Relationships" (PDF). Proceedings of the First Symposium on Bioinformatics and Biotechnology (BIOT-04). Retrieved 2016-09-03.
Jump up ^ Carrel L, Willard H (2005). "X-inactivation profile reveals extensive variability in X-linked gene expression in females". Nature. 434 (7031): 400–4. doi:10.1038/nature03479. PMID 15772666.
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.
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Jump up ^ "Search results - X[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 - X[CHR] AND "Homo sapiens"[Organism] AND ("genetype pseudo"[Properties] AND alive[prop]) - Gene". NCBI. 2017-05-19. Retrieved 2017-05-20.
Jump up ^ Ross M, et al. (2005). "The DNA sequence of the human X chromosome". Nature. 434 (7031): 325–37. doi:10.1038/nature03440. PMC 2665286  . PMID 15772651.
Jump up ^ Harold Chen; Ian Krantz; Mary L Windle; Margaret M McGovern; Paul D Petry; Bruce Buehler (2013-02-22). "Klinefelter Syndrome Pathophysiology". Medscape. Retrieved 2014-07-18.
Jump up ^ Visootsak J, Graham JM (2006). "Klinefelter syndrome and other sex chromosomal aneuploidies". Orphanet J Rare Dis. 1: 42. doi:10.1186/1750-1172-1-42. PMC 1634840  . PMID 17062147.
Jump up ^ Bender B, Puck M, Salbenblatt J, Robinson A (1986). Smith S, ed. Cognitive development of children with sex chromosome abnormalities. San Diego: College Hill Press. pp. 175–201.
Jump up ^ "Triple X syndrome". Genetics Home Reference. 2014-07-14. Retrieved 2014-07-18.
^ Jump up to: a b Skuse, David H. (2005-04-15). "X-linked genes and mental functioning". Human Molecular Genetics. 14 Spec No 1: R27–32. doi:10.1093/hmg/ddi112. ISSN 0964-6906. PMID 15809269.
Jump up ^ Zhao, Min; Kong, Lei; Qu, Hong (2014-02-25). "A systems biology approach to identify intelligence quotient score-related genomic regions, and pathways relevant to potential therapeutic treatments". Scientific Reports. 4. doi:10.1038/srep04176. ISSN 2045-2322. PMC 3933868  . PMID 24566931.
Jump up ^ Startin, Carla M.; Fiorentini, Chiara; de Haan, Michelle; Skuse, David H. (2015-01-01). "Variation in the X-linked EFHC2 gene is associated with social cognitive abilities in males". PLOS ONE. 10 (6): e0131604. doi:10.1371/journal.pone.0131604. ISSN 1932-6203. PMC 4481314  . PMID 26107779.
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.
Jump up ^ "p": Short arm; "q": Long arm.
Jump up ^ For cytogenetic banding nomenclature, see article locus.
^ Jump up to: a b 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.
External links[edit]
Wikimedia Commons has media related to X chromosomes.
National Institutes of Health. "X chromosome". Genetics Home Reference. Retrieved 2017-05-06.
"X chromosome". Human Genome Project Information Archive 1990–2003. Retrieved 2017-05-06.
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Retrieved from "https://en.wikipedia.org/w/index.php?title=X_chromosome&oldid=819436740"
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