A high salt level indicates CF. During pregnancy, an accurate diagnosis of cystic fibrosis in the fetus is usually possible. In males who have only one X chromosome , one altered copy of the gene in each cell is sufficient to cause the condition. ABO blood group, alpha-1 antitrypsin deficiency Mitochondrial Mitochondrial inheritance , also known as maternal inheritance, applies to genes in mitochondrial DNA. In males who have only one X chromosome , a mutation in the only copy of the gene in each cell causes the disorder. For an example, please see What are genomic imprinting and uniparental disomy? Symptoms vary from person to person, in part, due to the more than 1, mutations of the CF gene, several of which have been identified and sequenced by researchers. Many people even live into their fifties and sixties. Genetic testing on a small blood sample can help determine who has a defective cystic fibrosis gene. Pulmonary function tests may show that breathing is compromised. The Centre for Genetics Education provides information about many of the inheritance patterns outlined above: Unless both parents have at least one such gene, their children will not have cystic fibrosis. Autosomal recessive disorders are typically not seen in every generation of an affected family. An individual must inherit two defective cystic fibrosis genes, one from each parent, to have the disease. If pancreatic enzyme levels are reduced, an analysis of the person's stool may reveal decreased or absent levels of the digestive enzymes trypsin and chymotrypsin or high levels of fat. Also, a chest x-ray may suggest the diagnosis. This simple and painless procedure measures the amount of salt in the sweat.