Researchers have tracked down a pair of genes that, together, seem responsible for some insects' ability to sense carbon dioxide. Because mosquitoes detect the gas to home in on their next blood meal, a means to block this sense could lead to more-effective mosquito repellents.
To locate the carbon dioxide–sensing genes, Leslie Vosshall of the Rockefeller Institute in New York and her colleagues worked with Drosophila melanogaster. Other researchers had previously found that carbon dioxide–sensing cells in this fruit fly's antennae express a gene known as gustatory receptor 21a (Gr21a). Using a genetic test, Vosshall's team discovered that these cells also express a related gene known as Gr63a.
To see whether the two genes play a role in carbon dioxide detection, the researchers inserted them into fruit fly neurons that normally respond to fruit odors but not to carbon dioxide. When the researchers placed both genes into the neuron