Cystic Fibrosis: Describe the type of genetic defect that causes this disease (E
ID: 16899 • Letter: C
Question
Cystic Fibrosis:Describe the type of genetic defect that causes this disease (Ex. Base deletion, base addition, base substitution, frame shift, non-disjunction, etc).
What type of inheritance pattern does it have? (Ex. Autosomal dominate, autosomal recessive, X-linked recessive, etc)
Explain the express of the disease in the cell membrane. (Hint: What is the normal role of this protein? Where do you find it in the cell? How does the mutation change its function? Why does this change in function occur?
List problems that are caused by this disease (Be specific in the types of problems that occur. Do these problems lead to other problems? What organs are affected?
Explanation / Answer
Cystic fibrosis is an inherited disease of the mucus glands that affects many body systems. The disorder's most common signs and symptoms include progressive damage to the respiratory system and chronic digestive system problems.
Mucus is a slippery substance that lubricates and protects the linings of the airways, digestive system, reproductive system, and other organs and tissues. In people with cystic fibrosis, the body produces mucus that is abnormally thick and sticky. This abnormal mucus can obstruct the airways, leading to severe problems with breathing and bacterial infections in the lungs. These infections cause chronic coughing, wheezing, and inflammation. Over time, mucus buildup and infections result in permanent lung damage, including the formation of scar tissue (fibrosis) and cysts in the lungs.
Most people with cystic fibrosis also have digestive problems because thick, sticky mucus interferes with the function of the pancreas. The pancreas is an organ that produces insulin (a hormone that helps control blood sugar levels). It also makes enzymes that help digest food. In people with cystic fibrosis, mucus blocks the ducts of the pancreas, preventing these enzymes from reaching the intestines to aid digestion. Problems with digestion can lead to diarrhea, malnutrition, poor growth, and weight loss. Some babies with cystic fibrosis have meconium ileus, a blockage of the intestine that occurs shortly after birth.
Cystic fibrosis used to be considered a fatal disease of childhood. With improved treatments and better ways to manage the disease, many people with cystic fibrosis now live well into adulthood. Adults with cystic fibrosis experience medical problems affecting the respiratory, digestive, and reproductive systems. For example, most men with cystic fibrosis are unable to father children (infertile) because the tubes that carry sperm (the vas deferens) are blocked by mucus and do not develop properly. This condition is known as congenital bilateral absence of the vas deferens (CBAVD). Infertility is also possible, though less common, in women with cystic fibrosis.
Mutations in the CFTR gene cause cystic fibrosis.
The CFTR gene provides instructions for making a channel that transports negatively charged particles called chloride ions into and out of cells. The flow of chloride ions helps control the movement of water in tissues, which is necessary for the production of thin, freely flowing mucus.
Mutations in the CFTR gene disrupt the function of the chloride channels, preventing them from regulating the flow of chloride ions and water across cell membranes. As a result, cells that line the passageways of the lungs, pancreas, and other organs produce mucus that is unusually thick and sticky. This mucus clogs the airways and glands, causing the characteristic signs and symptoms of cystic fibrosis.
Other genetic and environmental factors likely influence the severity of the condition. For example, mutations in genes other than CFTR might help explain why some people with cystic fibrosis are more severely affected than others. Most of these genetic changes have not been identified, however.
Read more about the CFTR gene.
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