On Nov. 19, 2001, researchers at Lucile Packard Children’s Hospital at Stanford announced they had identified a novel gene family that appears critical to the development of asthma in mice.

Using a technique known as backcrossing, McIntire and her colleagues generated mice that were genetically identical to the susceptible mice, other than for small segments of DNA from the resistant group. They then looked for mice in the group that did not develop AHR when exposed to an allergen.

They found that mice containing a small segment of DNA similar to an asthma susceptibility region on human chromosome 5 were significantly less likely to develop AHR than the susceptible group, even though the two groups shared the rest of their genomes.