X染色体
性染色體存在於物種的兩種性別中,其中雄性是異配性。 雌性的每個體細胞中都有兩個X染色體拷貝,雄性中有一個拷貝。 / 维基百科,自由的 encyclopedia
X染色体(英语:X chromosome)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(英语: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
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(但可透过后天培养而纠正),平均智力为90,较正常的100为低。她们能正常生育。[1]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
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XB表示正常基因,以Xb表示带病基因,则男性病者表示为XbY,辨色能力正常者为XBY;女性病者表示为XbXb,带因者为XBXb,功能正常亦非带因者为XBXB。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(XbY,XbXb)
- 儿子为XbY,女儿为XbXb,即子代都是病者。
- 父亲正常,母亲为病者(XBY,XbXb)
- 儿子为XbY,女儿为XBXb,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XbY,母亲为XBXB
- 儿子为XBY,女儿为XbXB,即儿子正常,女儿为带因者。
- 父亲为XbY,母亲为XBXb
- 儿子XBY或XbY,女儿为XBXb或XbXb,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。
- 父亲为XbY,母亲为XBXB
- 父母均正常(两种情况)
- 父亲为XBY,母亲为XBXB
- 儿子为XBY,女儿为XBXB,即子代都正常。
- 父亲为XBY,母亲为XBXb
- 儿子为XBY或XbY,女儿为XBXB或XBXb,即儿子有50%的概率为病者,女儿有50%的概率为带因者。
- 父亲为XBY,母亲为XBXB
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
- 裂颚
- 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:
注释
- Genome Decoration Page, NCBI. Ideogram data for Homo sapience (400 bphs, Assembly GRCh38.p3) (页面存档备份,存于互联网档案馆). 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,存于互联网档案馆). 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,存于互联网档案馆). Last update 2014-06-03. Retrieved 2017-04-26.
- International Standing Committee on Human Cytogenetic Nomenclature. ISCN 2013: An International System for Human Cytogenetic Nomenclature (2013). Karger Medical and Scientific Publishers. 2013. ISBN 978-3-318-02253-7.
- Sethakulvichai, W.; Manitpornsut, S.; Wiboonrat, M.; Lilakiatsakun, W.; Assawamakin, A.; Tongsima, S. Estimation of band level resolutions of human chromosome images. 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)