Researchers in the UK have uncovered a new gene that triggers asthma. Bill Cookson and colleagues, from London's Imperial College, compared the genes of 1000 children with asthma and 1000 healthy "controls" to track down genes that were more common in the asthmatics and might therefore provoke the condition. To do this the team used a system of genetic markers called SNPs or single nucleotide polymorphisms. These flag up certain genetic sequences. So by analysing large numbers of people with a disease, and comparing them with people who don't have the condition, you can see SNPs, and hence DNA hotspots, that crop up more often in the diseased individuals than in the healthy ones. Using this technique the team were able to home in on several DNA hotspots on chromosome 17, and also identify a new gene, called ORMDL3, which was much more common in the children with asthma than the healthy controls. "This gene occurs in about 30% of children with asthma," says Cookson. "It seems to have a fundamental role in the working of the immune system, but we don't know what it does yet". So the next step will be to study where in the body it operates and how it works. This could well open up new avenues for the treatment or even prevention of asthma. But the fact that only 30% of the asthmatic children were carrying it shows that there's much more to asthma than just genetics, and that mystery still needs to be solved.