'Jumping genes', or transposable elements, are tracts of DNA that can move around in the genome and are thought to offer potential for rapid rewiring of gene-regulatory networks. Researchers have found evidence of this in medaka fish (Oryzias latipes).
About 10 million years ago in an ancestor of the medaka fish, a gene called dmrt1a — which occurs downstream in a sex-determination cascade — duplicated. One copy, dmrt1bY, later became a master 'maleness' regulator at the top of the cascade. To figure out how this happened, Amaury Herpin of the University of Würzburg in Germany and his colleagues analysed the regulatory region of dmrt1bY.
They found that a mobile piece of DNA had inserted into this region shortly after the gene duplication. Both the Dmrt1a and Dmrt1bY proteins bind to this transposable element to reduce expression of the dmrt1bY gene. This suggests that insertion of the mobile DNA rewired this gene network.