Here is an example of a genetic mutation on chromosome 7. The lung-disorder cystic fibrosis is associated with mutations in the CFTR gene, the cystic fibrosis transmembrane conductance regulator gene. In healthy lungs CFTR, which is an ion channel, allows the movement of chloride in and out of the cell, whereas in cystic fibrosis this chloride movement cannot occur and results in the build up of sticky mucus within the lung. The gene is located on 7Q31.2 and we can pinpoint this on chromosome 7. So Q means the long arm, 3 means region 3, 1 means band 1 and the 0.2 denotes subband 2.