U.S. researchers say a study of the genetic code for asthma in African-Americans could reveal why the disease disproportionately afflicts that population. Scientists at Johns Hopkins, with $9.5 million in funding from the National Heart, Lung and Blood Institute, will examine how hereditary factors affect African-Americans who have the disease, The Baltimore Sun reported Thursday. \"It would be the largest and most comprehensive study to identify genes and rare genetic variants of interest for asthma in African-Americans,\" James Kiley, the director of lung disease research for the institute, said. Asthma, which causes wheezing and difficulty in breathing, can lead to death if not treated. The Johns Hopkins team will include experts in genetics, immunology, epidemiology and allergic disease. Nationwide, about 20 percent of African-Americans have asthma, and black Americans are more likely than whites to die from asthma or end up in the emergency room, the Sun reported.