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微染色体

维基百科,自由的百科全书
鸡的染色体核型图,箭头所指为大型染色体上经染色的基因条带,点状结构则为微染色体

微染色体(Microchromosome)是鸟类与部分爬行类两生类鱼类细胞中一类较小的染色体,其中以鸟类的微染色体数量最多,鸟类通常具有约2n = 80条(40对)染色体,其中仅7至10对染色体为易于鉴别的大型染色体(包括性染色体),其他均为微染色体[1]隼形目鹦形目鸟类的一些微染色体彼此融合,因此染色体的总数较少[2][3]哺乳类[注 1]蛙类则无微染色体[6]。有研究发现有些龟鳖类(刺鳖英语Spiny softshell turtle中华鳖)决定性别的ZW/ZZ染色体为微染色体[7]

微染色体的长度通常小于20Mb[8] ,这些染色体在核型分析中较难鉴别,在有丝分裂中期英语metaphase大小仅有约1微米,且难以观察到中节与染色条带[6]。微染色体上带有许多基因,例如基因组中有50%至75%的基因位于微染色体上[9]。微染色体可能是由大型染色体形成的碎片演化而来[10]

注脚

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  1. ^ 少数唐氏症X染色体易裂症等染色体异常疾病患者细胞中多出的小型染色体有时也被称为微染色体[4][5]

参考文献

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  1. ^ O'Connor RE, Kiazim L, Skinner B, Fonseka G, Joseph S, Jennings R; et al. Patterns of microchromosome organization remain highly conserved throughout avian evolution.. Chromosoma. 2019, 128 (1): 21–29. PMC 6394684可免费查阅. PMID 30448925. doi:10.1007/s00412-018-0685-6. 
  2. ^ Nishida-Umehara C, Tsuda Y, Ishijima J, Ando J, Fujiwara A, Matsuda Y; et al. The molecular basis of chromosome orthologies and sex chromosomal differentiation in palaeognathous birds.. Chromosome Res. 2007, 15 (6): 721–34. PMID 17605112. doi:10.1007/s10577-007-1157-7. 
  3. ^ Nishida C, Ishijima J, Kosaka A, Tanabe H, Habermann FA, Griffin DK; et al. Characterization of chromosome structures of Falconinae (Falconidae, Falconiformes, Aves) by chromosome painting and delineation of chromosome rearrangements during their differentiation.. Chromosome Res. 2008, 16 (1): 171–81. PMID 18293111. doi:10.1007/s10577-007-1210-6. 
  4. ^ Ramos C, Rivera L, Benitez J, Tejedor E, Sanchez-Cascos A. Recurrence of Down's syndrome associated with microchromosome.. Hum Genet. 1979, 49 (1): 7–10. PMID 157321. doi:10.1007/BF00277682. 
  5. ^ López-Pajares I, Delicado A, Pascual-Castroviejo I, López-Martin V, Moreno F, Garcia-Marcos JA. Fragile X syndrome with extra microchromosome.. Clin Genet. 1994, 45 (4): 186–9. PMID 8062436. doi:10.1111/j.1399-0004.1994.tb04020.x. 
  6. ^ 6.0 6.1 Fillon, Valérie. The chicken as a model to study microchromosomes in birds: a review. Genetics Selection Evolution. 1998, 30 (3): 209. ISSN 1297-9686. doi:10.1186/1297-9686-30-3-209. 
  7. ^ Badenhorst D, Stanyon R, Engstrom T, Valenzuela N. A ZZ/ZW microchromosome system in the spiny softshell turtle, Apalone spinifera, reveals an intriguing sex chromosome conservation in Trionychidae.. Chromosome Res. 2013, 21 (2): 137–47. PMID 23512312. doi:10.1007/s10577-013-9343-2. 
  8. ^ Axelsson, Erik; Webster, Matthew T.; Smith, Nick G. C.; Burt, David W.; Ellegren, Hans. Comparison of the chicken and turkey genomes reveals a higher rate of nucleotide divergence on microchromosomes than macrochromosomes. Genome Research. 2005, 15 (1): 120–5. PMC 540272可免费查阅. PMID 15590944. doi:10.1101/gr.3021305. 
  9. ^ McQueen, Heather A.; Siriaco, Giorgia; Bird, Adrian P. Chicken microchromosomes are hyperacetylated, early replicating, and gene rich. Genome Research. 1998, 8 (6): 621–30. PMC 310741可免费查阅. PMID 9647637. doi:10.1101/gr.8.6.621. 
  10. ^ Burt, D.W. Origin and evolution of avian microchromosomes. Cytogenetic and Genome Research. 2002, 96 (1–4): 97–112. PMID 12438785. doi:10.1159/000063018.