How the pathophysiology is accquired

Cystic fibrosis is a genetic disease.  This means that the basis for developing CF is inherited from parents. As stated in earlier posts, a defect in the CFTR gene is what causes the development of CF.  Remember that the CFTR gene codes for the protein that controls ion, salt, and water movement out of the body's cells.

Each child receives two CFTR genes, one from each parent.  If the child receives only one faulty CFTR gene, they are considered a carrier. Carriers usually do not have any symptoms of CF, but they have the risk of passing it on to their children one day.  If the child inherits two faulty CFTR genes, the child will have cystic fibrosis.  This is called an autosomal recessive disease.  For the person to develop the disease, both copies of the defective gene must be present. 

This picture shows how the genes can be passed on from the parents.  There is a 25% chance (1 out of 4) that the child can inherit two normal genes or two faulty genes, and there is a 50% chance (2 out of 4) that can inherit one faulty and one normal gene.

Resources:
http://hihg.med.miami.edu/code/http/modules/education/Design/Print.asp?CourseNum=1&LessonNum=3
http://www.nhlbi.nih.gov/health/health-topics/topics/cf/causes.html