X染色体

X染色体
物种	Homo sapiens
基因数量	900-1200

X染色体（英语：）是部分动物决定性别的染色体之一。它出现在X0性别决定系统和XY性别决定系统中。对一般人类来说，女性有两条X染色体，男性X、Y染色体各有一条。

Hermann Henking发现了X染色体

人类

在人类约20,000至25,000个基因之中，X染色体约有2,000个基因。

一般女性有两条X染色体，其中一条会惰性化，变成巴尔体（Barr body），这个作用称为X去活性（X inactivation）或里昂化作用（lyonization，以发现者Mary F. Lyon命名）。（参见：三色猫）不论生物遗传了几个X染色体，都只有一个X染色体会活性化，其余皆惰性化，使生物能正常发挥功能，并具有修复功能。

细胞遗传带

人类X染色体G显带条状表意图

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,[1] 550[2] and 850[3]). Band length in this diagram is based on the ideograms from ISCN (2013).[4] This type of ideogram represents actual relative band length observed under a microscope at the different moments during the mitotic process.[5]

人类X染色体G显带分辨率850bph[3]
Chr.	Arm[6]	Band[7]	ISCN start[8]	ISCN stop[8]	Basepair start	Basepair stop	Stain[9]	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

疾病

因X染色体数目异常而出现的疾病：

X-三体：女性有三条X染色体。她们发展较迟缓（但可通过后天培养而纠正），平均智力为90，较正常的100为低。她们能正常生育。在罕见的情况下会出现如XXXX或XXXXX。
克氏综合症：男性有两条X染色体。他们的睾酮水平可能较低，胸部发育接近女性。罕见的情况下会出现XXXY或XXXXY。
透纳氏症（Turner syndrome）：女性只有一条X染色体。她们身材较矮小，性功能不能正常发展。

遗传病

左一：100%，左二：100%，左三：50%，左四：0%，换言之，男：50%：女75%。

X性联隐性遗传病是指一个人所有的X染色体都有带病基因时才会发生的疾病。男性患上这些疾病的机会都比女性高，因为男性只有一条X染色体，而女性有两条。若女性其中一条有带病基因，另一条仍可以发挥作用，但可能也会有较轻微的症状出现，因为在每个细胞内去活性化的X染色体都是随机决定的，若在负责带病基因相关功能的细胞内去活性化的为带正常基因的染色体，就会有轻微的症状出现，例如带有色盲致病基因的女性，若在视网膜组织内有较多的带正常基因X染色体不活化，则该女性的辨色力会比基因型完全正常的女性要差。

若以X^B表示正常基因，以X^b表示带病基因，则男性病者表示为X^bY，辨色能力正常者为X^BY；女性病者表示为X^bX^b，带因者为X^BX^b，功能正常亦非带因者为X^BX^B。排除子代发生基因突变的情况下，子代与父母辨色能力的关系如下：

父母均为病者（X^bY，X^bX^b）
儿子为X^bY，女儿为X^bX^b，即子代都是病者。
父亲正常，母亲为病者（X^BY，X^bX^b）
儿子为X^bY，女儿为X^BX^b，即儿子都是病者，女儿为带因者。
父亲为病者，母亲正常（两种情况）
- 父亲为X^bY，母亲为X^BX^B
  儿子为X^BY，女儿为X^bX^B，即儿子正常，女儿为带因者。
- 父亲为X^bY，母亲为X^BX^b
  儿子X^BY或X^bY，女儿为X^BX^b或X^bX^b，即儿子有50%的概率为病者，女儿必为带因者，而其中有50%的几率为病者。
父母均正常（两种情况）
- 父亲为X^BY，母亲为X^BX^B
  儿子为X^BY，女儿为X^BX^B，即子代都正常。
- 父亲为X^BY，母亲为X^BX^b
  儿子为X^BY或X^bY，女儿为X^BX^B或X^BX^b，即儿子有50%的概率为病者，女儿有50%的概率为带因者。

常见的X性联隐性遗传病有：

重症肌无力
血小板减少症
痛风
SCID（先天性免疫缺乏症、泡泡儿）
眼球白化症
裂腭
肌肉萎缩症
血友病
色盲
ALD（肾上腺脑白质退化症）
G6PD（蚕豆症）
XLSA（含铁母细胞性贫血的一种）
X染色体易裂症
法布瑞氏症
爱伯症候群

此外，亦有显性遗传病，已知文献中，此遗传类型非常稀少。（父母任何一方为病患者便有可能传到后代）如：

色素失调症
维生素D型无效性佝偻病
CMTX（腓骨肌萎缩症的一种）
蕾特氏症(Rett Syndrome)

注释

Genome Decoration Page, NCBI. Ideogram data for Homo sapience (400 bphs, Assembly GRCh38.p3) （页面存档备份，存于）. Last update 2014-03-04. Retrieved 2017-04-26.
Genome Decoration Page, NCBI. Ideogram data for Homo sapience (550 bphs, Assembly GRCh38.p3) （页面存档备份，存于）. Last update 2015-08-11. Retrieved 2017-04-26.
Genome Decoration Page, NCBI. Ideogram data for Homo sapience (850 bphs, Assembly GRCh38.p3) （页面存档备份，存于）. Last update 2014-06-03. Retrieved 2017-04-26.
International Standing Committee on Human Cytogenetic Nomenclature. . Karger Medical and Scientific Publishers. 2013. ISBN 978-3-318-02253-7.
Sethakulvichai, W.; Manitpornsut, S.; Wiboonrat, M.; Lilakiatsakun, W.; Assawamakin, A.; Tongsima, S. . 2012: 276–282 [2020-02-10]. ISBN 978-1-4673-1921-8. doi:10.1109/JCSSE.2012.6261965. （原始内容存档于2021-03-11）. |journal=被忽略 (帮助)
"p": Short arm; "q": Long arm.
For cytogenetic banding nomenclature, see article locus.
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.
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.

参见

ZC4H2缺乏症(ZC4H2 deficiency)

外部链接

This article is issued from Wikipedia. The text is licensed under Creative Commons - Attribution - Sharealike. Additional terms may apply for the media files.

[400bphs-1] Genome Decoration Page, NCBI. Ideogram data for Homo sapience (400 bphs, Assembly GRCh38.p3) （页面存档备份，存于）. Last update 2014-03-04. Retrieved 2017-04-26.

[550bphs-2] Genome Decoration Page, NCBI. Ideogram data for Homo sapience (550 bphs, Assembly GRCh38.p3) （页面存档备份，存于）. Last update 2015-08-11. Retrieved 2017-04-26.

[850bphs-3] Genome Decoration Page, NCBI. Ideogram data for Homo sapience (850 bphs, Assembly GRCh38.p3) （页面存档备份，存于）. Last update 2014-06-03. Retrieved 2017-04-26.

[Nomenclature2013-4] International Standing Committee on Human Cytogenetic Nomenclature. . Karger Medical and Scientific Publishers. 2013. ISBN 978-3-318-02253-7.

[SethakulvichaiManitpornsut2012-5] Sethakulvichai, W.; Manitpornsut, S.; Wiboonrat, M.; Lilakiatsakun, W.; Assawamakin, A.; Tongsima, S. . 2012: 276–282 [2020-02-10]. ISBN 978-1-4673-1921-8. doi:10.1109/JCSSE.2012.6261965. （原始内容存档于2021-03-11）. |journal=被忽略 (帮助)

[6] "p": Short arm; "q": Long arm.

[7] For cytogenetic banding nomenclature, see article locus.

[ISCN-8] 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.

[9] 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.

X染色体

物种	Homo sapiens
基因数量	900-1200