Cystic fibrosis (CF) is a genetically inherited disease of the secretory
glands that primarily affects the lungs, digestive
system, and the pancreas of about 30,000 children
and adults living in the United States. CF is caused
by a mutation in
the cystic
fibrosis transmembrane conductance regulator (CFTR) gene. Normally
this gene makes a protein that facilitates the
regulated transport of salt and water in and out
of human cells. In contrast, the CF gene produces
thick, sticky secretions (mucous) in the respiratory
and digestive tracts, as well as in the reproductive
system. Additionally, this process causes a measurable
increase in salt excreted in sweat.
Accumulation of mucous can build up in the lungs of individuals with
CF. This buildup makes it easy for bacteria to
grow and can lead to recurring lung infections. This
thick, sticky mucus can also block tubes, or ducts,
in the pancreas. As a result, digestive enzymes that
are produced by the pancreas cannot reach the small
intestine. These enzymes normally help in the process
of digestion. Without these enzymes, the intestines
cannot adequately absorb fats and proteins.
The CF gene, which is inherited from a child's parents, is an autosomal
recessive gene. With recessive genes, children need
to inherit two copies of the gene, one from each
parent, in order to have CF. If children inherit
only one copy, they won't develop cystic fibrosis,
but can be carriers and possibly pass the gene
to their own children. Carriers of the CF gene
may never realize that they possess a copy of the
gene since they will not be symptomatic.
If two people who carry the defective gene conceive a child, there's
a 25 percent chance the child will have CF, a 50
percent chance the child will be a carrier of the
cystic fibrosis gene, and a 25 percent chance the
child will neither have the disease nor be a carrier.
Key: □ = male, o = female
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About Cystic Fibrosis
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