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首页> 外文期刊>Genetica >Molecular cytogenetics and characterization of a ZZ/ZW sex chromosome system in Triportheus nematurus (Characiformes, Characidae)
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Molecular cytogenetics and characterization of a ZZ/ZW sex chromosome system in Triportheus nematurus (Characiformes, Characidae)

机译：Triportheus nematurus（Characiformes，Characidae）的ZZ / ZW性染色体系统的分子细胞遗传学和特征

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摘要

Chromosomes of Triportheus nematurus, a fish species from family Characidae, were analyzed in order to establish the conventional karyotype, location of C-band positive heterochromatin, Ag-NORs, GC- and AT-rich sites, and mapping of 18S and 5S rDNA with fluorescence in situ hybridization (FISH). The diploid number found was 2n = 52 chromosomes in both males and females. However, the females presented a pair of differentiated heteromorphic chromosomes, characterizing a ZZ/ZW sex chromosome system. The Z chromosome was metacentric and the largest one in the karyotype, bearing C-positive heterochromatin at pericentromeric and telomeric regions. The W chromosome was middle-sized submetacentric, appearing mostly heterochromatic after C-banding and presenting heterogeneous heterochromatin composed of GC- and AT-rich regions revealed by fluorochrome staining. Ag-NORs were also GC-rich and surrounded by heterochromatic regions, being located at the secondary constriction on the short arms of the second chromosome pair, in agreement with 18S rDNA sites detected with FISH. The 18S and 5S rDNA were aligned in tandem, representing an uncommon situation in fishes. The results obtained reinforce the basal condition of the ZZ/ZW sex system in the genus Triportheus, probably arisen prior to speciation in the group.
机译：为了确定常规核型，C带阳性异染色质，Ag-NORs，富含GC和AT的位点的位置，以及绘制18S和5S rDNA的图谱，分析了来自Characidae家族的鱼类Triportheus nematurus的染色体。荧光原位杂交（FISH）。男性和女性的二倍体数均为2n = 52条染色体。然而，雌性呈现出一对分化的异型染色体，表征了ZZ / ZW性染色体系统。 Z染色体是亚中心的，是核型中最大的，在着丝粒和端粒区域带有C阳性异染色质。 W染色体是中等大小的亚超中心基因，在C显带后主要表现为异色，并呈现由荧光染色显示的富含GC和AT的区域组成的异质异染色质。 Ag-NORs也富含GC，并被异色区包围，位于第二条染色体对短臂的次要缩颈处，与FISH检测到的18S rDNA位点一致。 18S和5S rDNA串联排列，这代表了鱼类中的罕见情况。获得的结果加强了Triportheus属中ZZ / ZW性系统的基础条件，这可能是在该物种形成之前出现的。

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