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染色体不分离

维基百科,自由的百科全书
1. 第一次减数分裂
2. 第二次减数分裂
3. 受精
4. 合子

左图的蓝色箭头指第二次减数分裂中发生染色体不分离,右图的绿色箭头指第一次减数分裂中发生染色体不分离

染色体不分离(Nondisjunction)是指生物细胞分裂时,同源染色体姊妹染色体未能成功分离的现象,由美国遗传学家卡尔文·布里基斯英语Calvin Bridges托马斯·亨特·摩尔根于1910年在黑腹果蝇细胞的性染色体上发现[1]。染色体不分离包括第一次减数分裂时同源染色体不分离、第二次减数分裂时姊妹染色体不分离、以及有丝分裂时姊妹染色体不分离等三种情形[2][3][4]

染色体不分离会造成子细胞成为非整倍体,即多出一条染色体或(2n+1)或失去一条染色体(2n-1)[4],若发生在减数分裂则可能造成子代发生非整倍体疾病,三体症(细胞具有3条该该对染色体)包括唐氏症爱德华氏症候群克氏综合征[3][5];已知的单体症英语Monosomy(细胞仅有1条该对染色体)则仅有透纳氏症一种[3][5]

人类的非整倍体疾病较多是女性减数分裂时(特别是第一次减数分裂[6])发生染色体不分离所致,可能原因是卵母细胞减数分裂过程中,会在前期I停滞数年至数十年之久,可能为使姊妹染色体失去黏连蛋白英语cohesin而相互分离,进而使著丝点连接错误[6][7],相较之下精母细胞则会快速地完成整个减数分裂流程;另外精母细胞减数分裂时发生染色体互换的频率高于卵母细胞,人类卵母细胞有超过10%有至少一对同源染色分体在联会过程中没有发生互换,而缺乏互换是造成染色体不分离的原因之一[8]。有些物质(非整倍体诱变剂英语aneugen)可以促使细胞分裂时发生染色体不分离的现象,烟草即为一种非整倍体诱变剂,因此吸烟会提升染色体不分离的机率[9][10];另有研究显示酒精[11][12]氰戊菊酯[13]甲萘威[14]等物质可能也是非整倍体诱变剂。

为避免细胞分裂时染色体不分离,细胞周期中有纺锤体组装检查点英语Spindle checkpoint(SAC)以确保细胞中染色体均与纺锤体连接妥当后才活化促后期复合体英语Anaphase-promoting complex(APC),使细胞分裂进入后期英语Anaphase[15]

参考文献

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  7. ^ Eichenlaub-Ritter, Ursula. Oocyte ageing and its cellular basis. The International Journal of Developmental Biology. 2012, 56 (10–11–12): 841–852. PMID 23417406. doi:10.1387/ijdb.120141ue可免费查阅. 
  8. ^ Nagaoka, SI; Hassold, TJ; Hunt, PA. Human aneuploidy: mechanisms and new insights into an age-old problem.. Nature Reviews Genetics. 2012-06-18, 13 (7): 493–504. PMC 3551553可免费查阅. PMID 22705668. doi:10.1038/nrg3245. 
  9. ^ Shi Q, Ko E, Barclay L, Hoang T, Rademaker A, Martin R. Cigarette smoking and aneuploidy in human sperm. Mol. Reprod. Dev. 2001, 59 (4): 417–21. PMID 11468778. S2CID 35230655. doi:10.1002/mrd.1048. 
  10. ^ Rubes J, Lowe X, Moore D, Perreault S, Slott V, Evenson D, Selevan SG, Wyrobek AJ. Smoking cigarettes is associated with increased sperm disomy in teenage men. Fertil. Steril. 1998, 70 (4): 715–23. PMID 9797104. doi:10.1016/S0015-0282(98)00261-1. 
  11. ^ Benassi-Evans B, Fenech M. Chronic alcohol exposure induces genome damage measured using the cytokinesis-block micronucleus cytome assay and aneuploidy in human B lymphoblastoid cell lines. Mutagenesis. 2011, 26 (3): 421–9. PMID 21273273. doi:10.1093/mutage/geq110可免费查阅. 
  12. ^ McHale CM, Smith MT, Zhang L. Application of toxicogenomic profiling to evaluate effects of benzene and formaldehyde: from yeast to human. Ann. N. Y. Acad. Sci. 2014, 1310 (1): 74–83. Bibcode:2014NYASA1310...74M. PMC 3978411可免费查阅. PMID 24571325. doi:10.1111/nyas.12382. 
  13. ^ Xia Y, Bian Q, Xu L, Cheng S, Song L, Liu J, Wu W, Wang S, Wang X. Genotoxic effects on human spermatozoa among pesticide factory workers exposed to fenvalerate. Toxicology. 2004, 203 (1–3): 49–60. PMID 15363581. doi:10.1016/j.tox.2004.05.018. 
  14. ^ Xia Y, Cheng S, Bian Q, Xu L, Collins MD, Chang HC, Song L, Liu J, Wang S, Wang X. Genotoxic effects on spermatozoa of carbaryl-exposed workers. Toxicol. Sci. 2005, 85 (1): 615–23. PMID 15615886. doi:10.1093/toxsci/kfi066可免费查阅. 
  15. ^ Sun, S.-C.; Kim, N.-H. Spindle assembly checkpoint and its regulators in meiosis. Human Reproduction Update. 2011-11-14, 18 (1): 60–72. PMID 22086113. doi:10.1093/humupd/dmr044可免费查阅.