Several types of genetic testing are done for different reasons: 1  Diagnostic testing. 2  If you have symptoms of a disease that may be caused by genetic alterations, genetic testing can reveal if you have the suspected disorder. If you have a family history of a genetic disorder — such as sickle cell anemia or cystic fibrosis — or you are in an ethnic group that has a high risk of a particular genetic disorder, you may choose to have genetic testing before you have children.