Cytogenetic characterization and description of an XX/XY1Y2 sex chromosome system in catfish Harttia carvalhoi (Siluriformes, Loricariidae)
Cytogenetic characterization and description of an XX/XY1Y2 sex chromosome system in catfish Harttia carvalhoi (Siluriformes, Loricariidae)
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DOI：
10.1159/000089887
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发表时间：
2006-01-01
影响因子：
1.7
通讯作者：
Moreira, O
中科院分区：
文献类型：
--
作者：
Centofante, L;Bertollo, LAC;Moreira, O
猫的核型和细胞遗传学特征。采用差异染色技术（c带、ag染色）和荧光原位杂交（fish），采用18S和5S rDNA探针对巴西圣保罗州Paraiba do Sul河流域的Harttia carvalhoi鱼进行了研究。雌性二倍体染色体数目为2n = 52，核型由9对稳心染色体、9对亚稳心染色体、4对亚远心染色体和4对远心染色体组成。雄性二倍体染色体数目均为2n = 53，核型为1对未配对的大异心染色体、8对异心染色体、9对亚异心染色体、4对亚异心染色体、4对顶心染色体和2对中等大小的顶心染色体。雌雄核型差异表明存在XX/XY1Y2型性染色体系统，其中X是最大的稳中心染色体，Y-1和Y-2是雄性核型中另外两条中间的外中心染色体。用FISH和18S rDNA探针发现的主要rDNA位点位于最大的一对顶心染色体的近中心区域。使用5S rDNA探针的FISH发现了两个位点：位于最大的一对单心染色体上的间隙位点和位于较小的双心染色体上的周着丝点位点。祖先2n = 54核型中的易位或中心融合被假设为这种多性染色体系统的起源，其中女性是固定易位纯合子，而男性是固定易位杂合子。到目前为止，对Harttia属的代表进行的细胞遗传学研究表明，该属具有很大的kayotype多样性。
Karyotypic and cytogenetic characteristics of cat. fish Harttia carvalhoi ( Paraiba do Sul River basin, Sao Paulo State, Brazil) were investigated using differential staining techniques ( C-banding, Ag-staining) and fluorescent in situ hybridization ( FISH) with 18S and 5S rDNA probes. The diploid chromosome number of females was 2n = 52 and their karyotype was composed of nine pairs of metacentric, nine pairs of submetacentric, four pairs of subtelocentric and four pairs of acrocentric chromosomes. The diploid chromosome number of males was invariably 2n = 53 and their karyotype consisted of one large unpaired metacentric, eight pairs of metacentric, nine pairs of submetacentric, four pairs of subtelocentric, four pairs of acrocentric plus two middle- sized acrocentric chromosomes. The differences between female and male karyotypes indicated the presence of a sex chromosome system of XX/XY1Y2 type, where the X is the largest metacentric and Y-1 and Y-2 are the two additional middlesized acrocentric chromosomes of the male karyotype. The major rDNA sites as revealed by FISH with an 18S rDNA probe were located in the pericentromeric region of the largest pair of acrocentric chromosomes. FISH with a 5S rDNA probe revealed two sites: an interstitial site located in the largest pair of acrocentric chromosomes, and a pericentromeric site in a smaller metacentric pair of chromosomes. Translocations or centric fusions in the ancestral 2n = 54 karyotype is hypothesized for the origin of such multiple sex chromosome systems where females are fixed translocation homozygotes whereas males are fixed translocation heterozygotes. The available cytogenetic data for representatives of the genus Harttia examined so far indicate large kayotype diversity.