written by: Finn Orfano•edited by: Leigh A. Zaykoski•updated: 1/31/2010
Cystic fibrosis is a disease that is inherited at birth, but it's not always detected right away. Why a person inherits cystic fibrosis depends on several variables.
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Cystic fibrosis, also known as CF, is a illness that affects the respiratory system. The illness causes respiratory failure and vitamin deficiencies. A major problem with CF is that is causes the secretions of the body to become thick and sticky, which clogs up passageways and create problems with the pancreas and lungs.
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The Cystic Fibrosis Gene
The defective gene of cystic fibrosis causes changes in the process of how salt moves in and out of a cell. This is because the protein responsible for this process is altered by the defective gene. This causes thick and sticky secretions to form in the respiratory system, digestive tract, and the reproductive system.
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Inheriting Cystic Fibrosis
The defective gene is recessive meaning that, for a person to inherit the gene, he must receive a copy from both parents. If a person only inherits one mutated CFTR (cystic fibrosis transmembrane regulator) gene, she can not inherit the disorder. The CFTR gene resides on chromosome 7.
The parents of a child that inherits cystic fibrosis do not have the disorder themselves. Instead the parents are called carriers. This is because they have a normal copy of the gene on their chromosome 7. The only time cystic fibrosis develops is when a child receives one mutated CFTR from his father and another mutated CFTR from his mother.
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The Odds of Inheriting Cystic Fibrosis
Children have a 25 percent chance of inheriting cystic fibrosis. Another 50 percent have a chance of carrying the recessive gene, but do not develop the disease. The remaining 25 percent do not inherit a mutated CFTR gene and do not carry the disease.
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Carriers of the Defective Gene
The carriers of the cystic fibrosis disorder lead very healthy and normal lives. The carriers show no signs or symptoms of the disorder and in, most cases, are not aware that they carry the gene. Genetic testing can be done to see if one is a carrier or not, but most people do not get this done unless cystic fibrosis runs in their family. If cystic fibrosis does run in the family, it is important to have yourself and your partner tested.
The test is performed by using a sample of blood or saliva. When the sample is analyzed, researchers can determine the presence of a mutated CFTR gene or the absence of a mutated CFTR gene. This test is used for family planning and genetic counseling purposes in people who desire children. If both parents carry a mutated CFTR gene, they may decide to adopt a child instead of taking the risk of having a child with cystic fibrosis. Unfortunately, this test is not always 100 percent accurate, meaning a person may get a normal result and still have the recessive mutated CFTR gene.