Department of Medical Cell Genetics, Medical Nobel Institute, Karolinska Institutet, S-104 01 Stockholm 60, Sweden.
EMBO J. 1983;2(7):1169-75. doi: 10.1002/j.1460-2075.1983.tb01563.x.
The internal structure of the 37 kb long Balbiani ring 2 (BR 2) gene in Chironomus tentans has been studied by analysis of a collection of cloned cDNA sequences and in genomic Southern blot analysis with the cDNA sequences used as probes. The BR 2 gene contains two types of tandemly arranged major repeat units 200 bp long, represented in our study by the pCt 7 and the pCt 63 cDNA inserts. The pCt 7 major repeat units are arranged in one or possibly a few blocks and cover 10 kb of the gene; the pCt 63 units form one uninterrupted block, 22 kb in length. Genomic Southern blot hybridizations revealed a number of sequence variants of the pCt 7 major repeat unit. In contrast, the 100 copies of the pCt 63 major repeat unit seem to be almost identical. The pCt 7 major repeat unit, 180 bp in length, is organized in the same way as the previously described 215 bp long pCt 63 major repeat, i.e., it contains a repetitive and a non-repetitive part. Moreover, the two major repeat units show a high degree of sequence homology, indicating that the pCt 7 and pCt 63 sequence blocks within the Br 2 gene have evolved through stepwise amplification from a common ancestral sequence.
摇蚊 Balbiani 环 2（BR 2）基因的内部结构已通过对一系列克隆 cDNA 序列的分析以及用 cDNA 序列作为探针的基因组 Southern 印迹分析进行了研究。BR 2 基因包含两种类型的串联排列的主要重复单元，长 200bp，在我们的研究中由 pCt 7 和 pCt 63 cDNA 插入物表示。pCt 7 主要重复单元排列成一个或几个块，覆盖基因的 10kb；pCt 63 单元形成一个不间断的 22kb 块。基因组 Southern 印迹杂交揭示了 pCt 7 主要重复单元的许多序列变体。相比之下，100 个 pCt 63 主要重复单元似乎几乎相同。pCt 7 主要重复单元长 180bp，其组织方式与先前描述的 215bp 长 pCt 63 主要重复单元相同，即它包含一个重复和一个非重复部分。此外，这两个主要重复单元显示出高度的序列同源性，表明 Br 2 基因内的 pCt 7 和 pCt 63 序列块是通过从共同祖先序列逐步扩增进化而来的。
