Melipona Illiger, 1806 is represented by 74 known species of stingless bees, distributed throughout the Neotropical region. Cytogenetically it is the most studied stingless bee genus of the tribe Meliponini. Member species are divided in two groups based on the volume of heterochromatin. This study aim was to analyze the composition and organization of chromatin of the stingless bee subspecies Melipona seminigra merrillae Cockerell, 1919 using classical and molecular cytogenetic techniques, so contributing to a better understanding of the processes of chromosomal changes within the genus. We confirm that M. seminigra merrillae has a chromosome number of 2n = 22 and n = 11, results that differ from those reported for the genus in the absence of B chromosomes. The heterochromatic pattern revealed a karyotype composed of chromosomes with a high heterochromatin content, which makes it difficult to visualize the centromere. Silver nitrate impregnation (Ag-NOR) showed transcriptionally active sites on the second chromosomal pair. Staining of base-specific fluorophores DAPI-CMA3 indicated a homogeneous distribution of intensely DAPI-stained heterochromatin, while CMA3 markings appeared on those terminal portions of the chromosomes corresponding to euchromatin. Similar to Ag-NOR, fluorescence in situ hybridization (FISH) with 18S ribosomal DNA probe revealed distinct signals on the second pair of chromosomes. Microsatellite mapping (GA)15 showed markings distributed in euchromatic regions, while mapping with (CA)15 showed marking patterns in heterochromatic regions, together with a fully marked chromosome pair. Microsatellite hybridization, both in heterochromatic and euchromatic regions, may be related to the activity of transposable elements. These are capable of forming new microsatellites that can be dispersed and amplified in different regions of the genome, demonstrating that repetitive sequences can evolve rapidly, thus resulting in within-genus diversification.

中文翻译：

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苜蓿半叶美lip科克内尔中重复DNA的染色体作图，1919年（膜翅目，Ap科，Meliponini）

Melipona Illiger（1806年）以74种已知的无刺蜂物种为代表，分布在整个新热带地区。在细胞遗传学上，它是Meliponini部落中研究最多的无刺蜂属。根据异染色质的体积将成员物种分为两组。这项研究的目的是使用经典和分子细胞遗传学技术分析无刺蜂亚种Melipona seminigra merrillae Cockerell，1919年的染色质的组成和组织，从而有助于更好地了解该属中染色体变化的过程。我们确认半裸M. merrillae具有2n = 22和n = 11的染色体数，其结果与报道的不存在B染色体的属的结果有所不同。异色模式揭示了由具有高异染色质含量的染色体组成的核型，这使得着丝粒的可视化变得困难。硝酸银浸渍（Ag-NOR）在第二对染色体上显示了转录活性位点。碱基特异性荧光团DAPI-CMA3的染色表明强DAPI染色的异染色质的均匀分布，而CMA3标记出现在与常染色质相对应的染色体末端部分。与Ag-NOR相似，使用18S核糖体DNA探针的荧光原位杂交（FISH）在第二对染色体上显示出不同的信号。微卫星测绘（GA）15显示标记分布在常色区域，而微卫星测绘（GA）15显示标记图案在异色区域，连同一个完全标记的染色体对。在异色和常色区域中的微卫星杂交都可能与转座因子的活性有关。它们能够形成新的微卫星，可以在基因组的不同区域中分散和扩增，这表明重复序列可以快速进化，从而导致属内多样化。