Sex chromosomes

A schematic view of the chromosome constitution (karyotype, 2n=46) of the Homo sapiens. There is the figure of XY and the XX chromosome in the lower right. Other chromosome autosome (2A).

The chromosome which the sex chromosomes (せいせんしょくたい) are dioecious creatures, and varies in a form and a number by the sex or the chromosome which a morphological difference is not seen, but participates in sex determination. I call the common chromosome autosome in the male females except sex chromosomes. ^{[* 1]} where not only the animal but also some plants have the distinction with sex chromosomes and the autosome.

When I clarify autosome and sex chromosomes and show chromosome constitution, I show one set of the autosome in sign A and transcribe it into 2n=2A+XY, n=A+Y.

Table of contents

Sex chromosomes and sex determination style

I refer to "the sex determination"

^{[* 2]} with four kinds of chromosomes named X,Y,Z,W as sex chromosomes. X and Y are names attached to the sex chromosomes observed by a sex determination method (male heteromodel :XY type) that a female has two X chromosomes toward, and Z and W are names of sex chromosomes observed by a sex determination method (female heteromodel :ZW type) that a male has two Z chromosomes. Y chromosome or W chromosome does not participate, and there is the sex determination style that an individual of the unilateral nature is decided only with X chromosome or one Z chromosome and shows that one of sex chromosomes does not exist at this time in sign O (male heteromodel :XO type, female heteromodel :ZO type). ^{[* 1][* 3]} where I have plural sex chromosomes classified in a similar kind in a normal individual by the creature, and (XnYn, ZnWn) exists.

In the mammals including the Homo sapiens, a male heteroXY type is common. With this sex determination style, the normal female is XX individual, and the normal male is XY individual. The XY type is observed with a sour sorrel and the evening campion with a part and the plant of the insect including the Drosophila elsewhere. As biology of another male heteromodel XO type, there are some mice [¹], nematode C. elegans, grasshopper.

As for the female heteromodel, a ZW type of birds, the Lepidoptera silkworm is a masterpiece. With this sex determination style, the normal female is ZW individual, and the normal male is ZZ individual. In the creatures of the ZO type such as parts of the fagot worm and the lizard, as for the male, two females have one Z chromosome.

There are most of the angiosperms and the hermaphroditism creature including the snail, and the nature is decided by temperature at the time of the embryo outbreak with a part of the reptiles such as crocodiles, and there is the straight foundation that sex chromosomes do not participate in decision.

A table.sex determination ^{[* 4} with sex chromosomes]

Sex chromosomes constitution		Animal	Plant
Male heteromodel	XY type A male: XY, female: XX	Most mammals Rainbow trout A part of the Diptera, the elytron eyes	Hop Hemp Evening campion
	XO type A male: XO, female: XX	Some mice C. elegans (in XX hermaphroditism) Orthopteran・Odonataなど
	Heteromorphic model (XnYn, XnO)	Duckmole (XnYn) Leatherfish (XnY) Mantis (XnY)	Sour sorrel (XYn) Empty Hana so (XnYn) Hop (XnYn)
Female heteromodel	ZW type A male: ZZ, female: ZW	Birds, snake Eel, Sea eel, Killifish Lepidoptera	Hawk strawberry (kind of the strawberry)
	ZO type A male: ZZ, female: ZO	Trichoptera, fagot worm	(do)
(the thing which sex chromosomes are hard to distinguish)		A part of the ranid (transition type of XY,ZW)	Kiwi fruit Yam Pistachio

The origin and change

Straight foundation not to have the sex chromosomes including the straight foundation and hermaphroditism creature class performing sex determination not to depend on sex chromosomes is mixed when I see the whole of the straight seed classified in same タクソン like a vertebrate and an angiosperm. This shows that sex chromosomes are not essential in expression of sex determination or the nature. In both the animal and the plant, it is thought that the sex chromosomes change from autosome, and was able to do it [²]; [³]. A gene about the sex determination comes to exist on the autosome, and it is in the origin of sex chromosomes that a chromosome having different genes came to receive the distribution that is different in the sex [²].

Of the amniote Ancestor type autosome (315 million years ago)	(166 million years ago)   Beast subclass Mammals (XY)   Monotreme (XY) (260 million years ago)   Birds (ZW)   Snakes (ZW)
A figure. Evolution of sex chromosomes in the amniote
I make it from Figure 4 of Fig.1 of Vallender and Lahn(2006)[2] and Veyrunes et al.(2008)[4]

^{[2][* 5]} where it is thought that the sex chromosomes of mammals and birds began differentiation with the autosome of the amniote (タクソン including mammals, birds, reptiles and the ancestor) from 10 million years to 300,002,000 years before approximately 300 million (the right figure). ^{[5][6][* 6]} which the homogeny of the sex chromosomes of mammals, birds, the snake suborder is low, and shows that I differentiated to sex chromosomes from different autosome each.

According to the study on monotreme duckmole sex chromosomes announced in 2008, as for the sex chromosomes of the duckmole, the homogeny with the sex chromosomes of marsupialia and beast subclass mammals is low, and the homogeny with the ZW sex chromosomes of birds is higher [⁴]. As for this, the sex chromosomes of a beast subclass and the monotreme show that it is another origin, and it is thought that it is in approximately 166 million years ago at the divergence time.

There is a plant species of the monoecism not to have sex chromosomes in a close species about the evening campion which is the sex-determining study in the angiosperm either. ^{[* 7]} where it is thought that it is thought that I evolved to dioecism through the plant of the satisfactory to both sides-related variant femininity from the monoecism plant of the ancestor type as for the evening campion, and the differentiation from autosome to sex chromosomes happened in this process. Dioecism ^{[* 7]} which is estimated when becoming it occurred with a different kind in the genus twice independently after the man trouble genus was established. ^{[* 7]} said to be an event at the estimated ^{[* 8]} time when it is done and is relatively newer than the establishment (before from 130 million years to 90 million years) of the angiosperm when the time is before from 24 million years to 8 million years.

It is thought about the change of sex chromosomes of the amniote as follows [²]. As for the sex chromosomes just after the differentiation, there was not a big difference other than genetic yes or no sex determination-related with neither sex chromosomes combination of XY, ZW from autosome. Although there were changes such as the acquisition of the mechanism to equate male and female gene expression, the Z chromosome which became the homology pair in the X chromosome which became the homology pair in females and males has been maintained about the size in the next evolution process by a structural change and dosage compensation such as the inversion. The hypothesis that the heredity information of X chromosome, the Z chromosome has been maintained at is proposed in 1967 by Kan Ono (law of Ono); [⁷].

On the other hand, the male Y chromosome of the amniote and the female W chromosome came to do the evolution that was different from X/Z chromosome because independent, one of them existed in the normal individual each. In general, ^{[2][8][* 9]} which the Y/W chromosome loses the gene which there is on the top, and tends to be downsized about the size. This tendency varies according to the kind of the amniote animal, and I include a tall and stout repetitive sequence in the Okinawa splinter mice and have a Y chromosome relatively big for mammals, and W chromosome and Z chromosome and the distinction in the form of the chromosome are included in the difficult example to ^{[* 10]}, birds ^{[* 11]}, reptiles [⁵] (example photograph halfpace Indian python ^[5] of snakes). In addition, ^{[* 7]} (photograph example ^[9]) where the thing which is bigger than an X chromosome is observed in the Y chromosome of the plant.

The domain where the homogeny called the para-autosome domain is left is to the mammalian X chromosome and Y chromosome, and the transfer gets up in the domain, too. The Y chromosome original constituted part comes to be accounted for by a large quantity of repetitive sequences. The W chromosome of birds leaves a lot of homology parts with the Z chromosome in comparison with mammalian Y and X chromosome [²].

^{[* 12]} [¹] where they lose a Y chromosome like アマミトゲネズミ and Tokuno sima splinter mouse about the downsizing of the mammalian Y chromosome, and sex constituted kind and ^{[* 10]} of XO having only an X chromosome together, the thing which similarly changed into XO-shaped sex determination method like the mole lemming included in the mouse superfamily exist. With these kinds, common sex determination gene SRY is lost in mammals, and it is thought that a different sex determination style to become the substitute produces it. ^{[* 13]} [⁴] where the SRY gene is not found in the monotreme either.

History of study

The chromosome was discovered as an intracellular structure dyed with a basic pigment in 1842 by curl ネーゲリ. It is ヴァルデヤー to have named the structure "chromosome (chromosom)" in 1888. A chromosome theory that a chromosome was a genetic carrier was proposed by Walter S Sutton in 1902, and I was demonstrated by about 1920 by Morgan.

^{[* 14]} where it was 1890 that I found the special chromosome which German biologist Hellman henKing did not prepare the pair with homologous chromosomes into unlike other chromosomes at the time of cell division with the testis cell of the harlequin bug (Hoshi harlequin bug). ^{[* 15]} where he named this chromosome X, but it became clear that the number that there was this X chromosome with the sex in the 1900s when a chromosome study progressed was a different sex chromosome.

^{[* 1]} [¹⁰] where the sex chromosomes of the plant were reported first in kind Spaerocarpos of the moss plant in 1917. ^{[* 1]} which evening campion, Winge discovered in hop Vallisneria asiatica evening campions in a sour sorrel as for the sex chromosomes of the seed plant independently each Canadian algae, Blackburn Santos Kihara and Ono in 1923.

I found a structure dyed in the nucleus that the Canadian neurobiologist Malaysia bar did not cause cell division in the nerve cells of the cat in 1949 densely. Because this structure which for each one per cell was included in was a female-specific as for him, I named this "a sex chromatin" (sex chromatin) [¹¹]. ^{[* 16]} which this "sex chromatin" would be called "a Barr body" generally, and came to be used by an examination of judgment of the sex. [* 17] which showed that two mammalian female X chromosomes looked like autosome as for one as for Kan Ono in 1959 and showed that the other cohered and was seen into a heterochromatin form [¹²], and a Barr body was one of two female X chromosomes in 1960. This phenomenon is called the inactivation of the X chromosome, and it is thought that it takes place for dosage compensation.

^{[* 5]} where it is thought that there is mechanism of the dosage compensation, and even the Z chromosome of birds equalizes genetic expression with the sex. However, ^{[* 5]} where it becomes clear that expression restraint is up in the chromosomal region which the mechanism is different from the inactivation of the mammalian X chromosome, and is relatively narrow or some genes.

Footnote

General footnote, Japanese documents

1. The ^ ^{a b c d} Chibu, Ono "sex determination and differentiation of the higher plant" ("recent biology" Vol. 4)
2. The name of ^ Z chromosome, the W chromosome is an X chromosome, a Y chromosome formally, but usually transcribes it each with Z W to facilitate the distinction of the male heteromodel, female heteromodel ("Iwanami biology dictionary").
3. The ^ Tokyo University of Agriculture and Technology department of agriculture silkworm studies laboratory "sex chromosomes of the insect"
4. "The Iwanami biology dictionary of ^ reference materials," it is made Chibu, Ono "sex determination of the higher plant and 31 pages of sex differentiation", the Matsunaga good luck size "sex determination mechanism of the higher plant" than the Chizuko Nishida "sex chromosomes evolution of birds" the Tokyo University of Agriculture and Technology department of agriculture silkworm studies laboratory "sex chromosomes of the insect"
5. ^ ^{a b c} Chizuko Nishida "sex chromosomes evolution "scientific heredity January, 2009 issue of the creature" of birds"
6. The ^ Matsubara sum pure; "differentiation process "scientific heredity January, 2009 issue of the creature" of the sex chromosomes in the snake"
7. ^ ^{a b c d} Matsunaga good luck size "sex determination mechanism "protein nucleic acid enzyme" Vol. 45 of the higher plant"
8. ^ PLoS Biology (2005). I describe it in "Evolution of Sex Chromosomes: The Case of the White Campion" with approximately 10 million years ago
9. ^ "thing 83-92 pages deciding a man and woman an X chromosome."
10. ^ ^{a b} Mari Kuroiwa "mammals which lost a Y chromosome, splinter mouse" "scientific heredity January, 2009 issue of the creature"
11. ^ eight cedar Ryuichi and others edition "sex determination" "Iwanami biology dictionary" (the fourth edition) - ostrich is raised for an example, but, according to the recent report (the Chizuko Nishida "sex chromosomes evolution of birds"), the distinction is possible.
12. ^ "thing 80-83 pages deciding a man and woman an X chromosome."
13. ^ "thing 79 pages deciding a man and woman an X chromosome."
14. ^ "thing 12-15 pages deciding a man and woman an X chromosome." The original papers is Henking, H(1891). L. Zeit. Wiss. Zool. 51.
15. ^ "thing 21-28 pages deciding a man and woman an X chromosome." The original papers is McLung CE(1901) Anatomischer Anzeinger 20:220, Steven NM(1905). at McLung CE(1902) Biological Bulletin 3:43 Journal of Experimental Zoology 2:371, Wilson EB(1905). Science 22:500.
16. ^ "thing 182-185 pages deciding a man and woman an X chromosome."
17. ^ "thing 185 pages deciding a man and woman an X chromosome." The original papers is Ohno S, Hauschka TS (1960). "Allocycly of the X-chromosome in tumors and normal tissues.". It is 541-545 Cancer Res 20. It is http://cancerres.aacrjournals.org/cgi/content/abstract/20/4/541. PMID 14428472 

English article

1. ^ ^{a b} Just W, Rau W, Vogel W, Akhverdian M, Fredga K, Graves JA, Lyapunova E (1995). "Absence of Sry in species of the vole Ellobius." It is doi:doi: 117-118 Nat Genet 11 10.1038/ng1095-117. PMID 7550333. 
2. ^ ^{a b c d e f g} Vallender EJ, Lahn BT (2006). "Multiple independent origins of sex chromosomes in amniotes". It is doi: 18,031-18,032 Proc Natl Acad Sci USA 103 10.1073/pnas.0608879103. http://www.pnas.org/content/103/48/18031.full March 30, 2009 reading. . 
3. ^ PLoS Biology (2005). "Evolution of Sex Chromosomes: The Case of the White Campion". It is e28. doi: PLoS Biol 3 10.1371/journal.pbio.0030028. http://biology.plosjournals.org/perlserv/?request=get-document&doi=10.1371%2Fjournal.pbio.0030028&ct=1 March 30, 2009 reading. . 
4. ^ ^{a b c} Veyrunes F, Waters PD, Miethke P, Rens W, McMillan D, Alsop AE, Grützner F, Deakin JE, Whittington CM, Schatzkamer K, Kremitzki CL, Graves T, Ferguson-Smith MA, Warren W, Marshall Graves JA (2008). "Bird-like sex chromosomes of platypus imply recent origin of mammal sex chromosomes". It is doi: 965-973 Genome Res 18 10.1101/gr.7101908. It is reading PMID 18463302 on http://genome.cshlp.org/content/18/6/965.full April 28, 2009. . 
5. ^ ^{a b c} Matsubara K, Tarui H, Toriba M, Yamada K, Nishida-Umehara C, Agata K, Matsuda Y (2006). "Evidence for different origin of sex chromosomes in snakes, birds, and mammals and step-wise differentiation of snake sex chromosomes". It is doi: 18,190-5 Proc Natl Acad Sci USA 103 10.1073/pnas.0605274103. It is reading PMID 17110446 on http://www.pnas.org/content/103/48/18190.full April 22, 2009. . 
6. ^ Matsuda Y, Nishida-Umehara C, Tarui H, Kuroiwa A, Yamada K, Isobe T, Ando J, Fujiwara A, Hirao Y, Nishimura O, Ishijima J, Hayashi A, Saito T, Murakami T, Murakami Y, Kuratani S, Agata K (2005). "Highly conserved linkage homology between birds and turtles: bird and turtle chromosomes are precise counterparts of each other". It is doi: 601-15 Chromosome Res 13 10.1007/s10577-005-0986-5. It is reading PMID 16170625 on http://eprints.lib.hokudai.ac.jp/dspace/handle/2115/30315 April 22, 2009. . 
7. ^ Ohno S (1967). Sex Chromosomes and sex-linked genes. Berlin:Springer-Verlag.
8. ^ Jegalian K, Page DC (1998). "A proposed path by which genes common to mammalian X and Y chromosomes evolve to become X inactivated." It is 776-80 Nature 394. PMID 9723615. 
9. ^ Matsunaga S (2009). "Junk DNA promotes sex chromosome evolution" (pdf). It is doi: 1-2 Heredity Heredity advance online publication, 1 April 2009 10.1038/hdy.2009.36. It is reading PMID 19337304 on http://www.nature.com/hdy/journal/vaop/ncurrent/pdf/hdy200936a.pdf April 22, 2009. . 
10. ^ Allen CE (1917). "A chromosome difference correlated with sex differences in Spaerocarpos." It is doi: 466-467 Science 46 10.1126/science.46.1193.466. PMID 17819473. 
11. ^ Barr ML, Bertram EG (1949). "A morphological distinction between neurones of the male and female, and the behaviour of the nucleolar satellite during accelerated nucleoprotein synthesis." Nature 163 (4148): 676–677. doi: 10.1038/163676a0. PMID 18120749. 
12. ^ Ohno S, Kaplan WD, Kinosita R (1959). "Formation of the sex chromatin by a single X-chromosome in liver cells of rattus norvegicus.." It is 415-419 Exp Cell Res 18. PMID 14428474. 

Reference materials

• For eight cedar Ryuichi and others edition "Iwanami biology dictionary" (the fourth edition) Iwanami Shoten, 1,996 years, it is ISBN 4-00-080087-6.
• It is 培風館, 30-47 pages, 1951 the Chibu, Ono "sex determination and differentiation of the higher plant" (Taku Komai, Hitoshi Kihara edition "biology Vol. 4 of these days").
• Tokyo University of Agriculture and Technology department of agriculture silkworm studies laboratory "sex chromosomes "sex determination" of the insect" (have a lot on the sex determination of a variety of animals except the insect). 2009-03-30 reading.
• In David Bainbridge "thing Kei Nagano deciding a man and woman an X chromosome", Akie Onoki (translation), Aoto Corporation, 2004, it is ISBN 978-4,791,761,524.
• "Scientific heredity special feature I "sex-determining genetics" January, 2009 issue of the creature", TNS.
  • Mari Kuroiwa "mammals which lost a Y chromosome, splinter mouse" 15-19 pages.
  • Chizuko Nishida "sex chromosomes evolution 20-25 pages of birds."
  • The Matsubara sum pure; 26-31 pages of "differentiation processes of the sex chromosomes in the snake."
  • Mitsuaki Ogata, Ikuo Miura "ranid 32-37 pages having two sex determination systems."
• Yoshitaka Nagahama, Tooru Kobayashi, Masaru Matsuda "sex differentiation "Japan Society for Comparative Endocrinology news in fish gonadal with sex determination"," it is 4-14 pages of Vol. 2003 (108).
• Matsunaga good luck size (2000) "sex determination mechanism "protein nucleic acid enzyme" Vol. 45 of the higher plant", Kyoritsu publishing company, 1704-1712 pages. 2009-04-02 reading.

Allied item

• Chromosome / autosome
• X chromosome / Y chromosome / Z chromosome / Inactivation of the X chromosome
• Sex determination / zoogamy

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