Dreesen T D, Bower J R, Case S T
J Biol Chem. 1985 Sep 25;260(21):11824-30.
A second gene has been discovered at a previously studied Balbiani ring in Chironomus. Northern hybridizations demonstrated that cDNA clone pCt35 originated from a salivary gland specific 6.5-kilobase (kb) RNA that was abundant, nonribosomal, and apparently poly(A)+. pCt35 had a 120-base pair (bp) insert with 1.6 copies of a 75-bp sequence that contained two open reading frames. Southern hybridizations indicated that pCt35 was homologous to at least a 4-kb block of genomic DNA organized as a hierarchy of 150- and 300-bp tandem repeats. In situ hybridization localized these sequences to Balbiani ring 1. From these results we postulated that a 6.5-kb RNA gene may have evolved by stepwise duplication and amplification of a 75-bp ancestral sequence.
在摇蚊先前研究过的一个巴尔比亚尼环中发现了第二个基因。Northern杂交表明，cDNA克隆pCt35源自一种唾液腺特异性的6.5千碱基（kb）RNA，该RNA含量丰富、非核糖体且显然是多聚腺苷酸化（poly(A)+）的。pCt35有一个120碱基对（bp）的插入片段，其中包含1.6个拷贝的75-bp序列，该序列含有两个开放阅读框。Southern杂交表明，pCt35与至少一个4-kb的基因组DNA区域同源，该区域由150-bp和300-bp的串联重复序列组成一个层级结构。原位杂交将这些序列定位到巴尔比亚尼环1。根据这些结果，我们推测一个6.5-kb的RNA基因可能是通过一个75-bp祖先序列的逐步重复和扩增而进化而来的。
