Considering that 2 metres of DNA fit into a cell nucleus a few micrometres across, you might think that the location of a gene on a chromosome would not be important. However, in the same way that microenvironments around cities affect local weather conditions, moving a gene to a new chromosomal neighbourhood can switch it on or off. Using flies and plants as model organisms, Gunter has identified proteins that enable different chromosomal neighbourhoods to switch genes on or off and he has found that such proteins are able to alter the packaging of DNA with its associated proteins.