Sümegi J, Wieslander L, Daneholt B
Cell. 1982 Sep;30(2):579-87. doi: 10.1016/0092-8674(82)90254-9.
One cloned cDNA sequence, pCt63, was used to characterize the repeated structure of the Balbiani ring 2 gene in Chironomus tentans. Although small in size (0.63 kb), the cDNA insert corresponds to a large portion (25 kb) of the BR2 gene (37 kb). Southern blotting experiments suggested that a large part of the BR2 gene consists of tandemly repeated units, each about 215 bp. Sequence analysis of the cDNA confirmed the repeated nature of the BR2 gene and revealed the internal structure of the repeat unit. Each such unit is composed of two regions of approximately equal length; one is highly ordered and built from about six 18 bp repeats, each consisting of a slightly diverged 9 bp duplication. The recorded hierarchic arrangement of the repetitive sequences in the BR2 gene and a specific pattern of base substitutions along the gene have enabled us to propose how a major part of the giant BR2 gene has evolved from a short primordial sequence, 110-120 bp in length.
一个克隆的cDNA序列pCt63被用于表征摇蚊Balbiani环2基因的重复结构。虽然该cDNA插入片段尺寸较小（0.63 kb），但它对应于BR2基因（37 kb）的很大一部分（25 kb）。Southern印迹实验表明，BR2基因的很大一部分由串联重复单元组成，每个单元约215 bp。cDNA的序列分析证实了BR2基因的重复性质，并揭示了重复单元的内部结构。每个这样的单元由两个长度大致相等的区域组成；一个是高度有序的，由大约六个18 bp的重复序列构成，每个重复序列由一个略有差异的9 bp重复片段组成。BR2基因中重复序列的层级排列记录以及该基因上碱基替换的特定模式，使我们能够提出这个巨大的BR2基因的主要部分是如何从一个长度为110 - 120 bp的短原始序列进化而来的。
