微染色体
微染色体（Microchromosome）是鸟类与部分爬行类、两生类及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]；隼形目和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]、鳄与蛙类则无微染色体[6]。有研究发现有些龟鳖类（刺鳖与中华鳖）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，在有丝分裂的中期大小仅有约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，例如鸡基因组中有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
参考文献
- ^ 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
. PMID 30448925. doi:10.1007/s00412-018-0685-6.
- ^ 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.
- ^ 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.
- ^ 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.
- ^ 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.
- ^ 6.0 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.
- ^ 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.
- ^ 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 . PMID 15590944. doi:10.1101/gr.3021305.
- ^ 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 . PMID 9647637. doi:10.1101/gr.8.6.621.
- ^ 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.
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