基因复制早就被认定为新基因和功能的一个来源，但大多数复制的基因没有新功能；它们只是将先祖基因的任务再分配。现在，研究人员对一例任务分配进行了详细分析。在酿酒酵母中，半乳糖利用通道包括两个非常相似的基因，编码一种共诱导因子（GAL3）和一种酶（GAL1）。二者是从一个双功能先祖基因传下来的，后者仍然见于其他酵母。两个原始基因之间可能的冲突已经解决，主要是由调控序列中所发生的一系列自适应变化来解决的。这种逐渐的退化花了近1亿年才完成，到GAL3完全失去半乳糖激酶活性才结束。GAL1 和 GAL3集成进了一个更复杂的、也可能更优化的基因通道中。
原始出处:
Nature 449, 677-681 (11 October 2007) | doi:10.1038/nature06151; Received 26 June 2007; Accepted 8 August 2007
Gene duplication and the adaptive evolution of a classic genetic switch
Chris Todd Hittinger1,2 & Sean B. Carroll1
Howard Hughes Medical Institute, Laboratory of Genetics, University of Wisconsin-Madison, 1525 Linden Drive, Madison, Wisconsin 53706, USA
Present address: Center for Genome Sciences, School of Medicine, Washington University in St Louis, 4444 Forest Park Avenue, St Louis, Missouri 63108, USA.
Correspondence to: Sean B. Carroll1 Correspondence and requests for materials should be addressed to S.B.C. (Email: sbcarrol@wisc.edu) and C.T.H. (Email: cthittinger@wustl.edu).
How gene duplication and divergence contribute to genetic novelty and adaptation has been of intense interest, but experimental evidence has been limited. The genetic switch controlling the yeast galactose use pathway includes two paralogous genes in Saccharomyces cerevisiae that encode a co-inducer (GAL3) and a galactokinase (GAL1). These paralogues arose from a single bifunctional ancestral gene as is still present in Kluyveromyces lactis. To determine which evolutionary processes shaped the evolution of the two paralogues, here we assess the effects of precise replacement of coding and non-coding sequences on organismal fitness. We suggest that duplication of the ancestral bifunctional gene allowed for the resolution of an adaptive conflict between the transcriptional regulation of the two gene functions. After duplication, previously disfavoured binding site configurations evolved that divided the regulation of the ancestral gene into two specialized genes, one of which ultimately became one of the most tightly regulated genes in the genome.
