Much of who we are biologically is determined by an interplay between our genes and the environment we live in. To learn how the transition of human populations from rural to urban lifestyles may be affecting the body's susceptibility to disease, researchers from North Carolina State University traveled to Morocco to study the genetic makeup of three communities living in three distinct environments: nomadic, rural, and urban.

Although the genes among the groups were quite similar, the expression of those genes-whether they're active or inactive-differed by up to 30 percent between urban and rural residents. Among the uniquely active genes in city dwellers were those that contribute to respiratory illnesses such as bronchitis or asthma. This suggests that environment can regulate the genetic basis of the immune system.

More fundamental changes of the genetic code-mutations-can also trigger respiratory illness. To learn more, view the Human Bulletin from April 21, 2008, "Scientists Pinpoint Genetic Link to Asthma."