Kwiatowski J, Krawczyk M, Kornacki M, Bailey K, Ayala F J
Institute of Botany, Warsaw University, Poland.
Proc Natl Acad Sci U S A. 1995 Aug 29;92(18):8503-6. doi: 10.1073/pnas.92.18.8503.
The exon theory of genes proposes that the introns of protein-encoding nuclear genes are remnants of the DNA spacers between ancient minigenes. The discovery of an intron at a predicted position in the triose-phosphate isomerase (EC 5.3.1.1) gene of Culex mosquitoes has been hailed as an evidential pillar of the theory. We have found that that intron is also present in Aedes mosquitoes, which are closely related to Culex, but not in the phylogenetically more distant Anopheles, nor in the fly Calliphora vicina, nor in the moth Spodoptera littoralis. The presence of this intron in Culex and Aedes is parsimoniously explained as the result of an insertion in a recent common ancestor of these two species rather than as the remnant of an ancient intron. The absence of the intron in 19 species of very diverse organisms requires at least 10 independent evolutionary losses in order to be consistent with the exon theory.
基因外显子理论提出，编码蛋白质的核基因中的内含子是古代小基因之间DNA间隔序列的残余物。在库蚊磷酸丙糖异构酶（EC 5.3.1.1）基因预测位置发现的一个内含子，被誉为该理论的一个证据支柱。我们发现，该内含子也存在于与库蚊亲缘关系密切的伊蚊中，但在系统发育上距离较远的按蚊中不存在，在丽蝇中不存在，在海滨夜蛾中也不存在。该内含子在库蚊和伊蚊中的存在，可以最简单地解释为是这两个物种最近共同祖先中发生插入的结果，而不是古代内含子的残余。在19种非常不同的生物中没有该内含子，这需要至少10次独立的进化丢失事件，才能与外显子理论相一致。
