Genetic Diseases

Genetic Diseases Genetic Diseases are very common and occur in various forms such as Cystic Fibrosis, Down’s syndrome, Sickle-cell Anaemia, Colour blindness, Haemophilia and others. This assignment will attempt to explain what Cystic Fibrosis is and how it has an effect on people. A genetic disease is a disease that is caused by an abnormality in an individual's DNA. Abnormalities can range from a small mutation in a single gene to the addition or subtraction of an entire chromosome or set of chromosomes. Cystic fibrosis (CF), also called mucoviscidosis, is a hereditary disease that affects the entire body, causing progressive disability and early death. It is the most common type of chronic lung disease in children and young adults. It is caused by a defect in the gene responsible for manufacturing Cystic Fibrosis Transmembrane Conductance Regulator (CFTR), a protein that controls the flow of chloride ions in and out of specific cells. Cystic fibrosis affects the entire body and impacts growth, breathing, digestion, and reproduction. For people with CF, malfunctioning CFTR prevents chloride from entering or leaving cells, and this results in the production of a thick, sticky mucus that clogs ducts or tubes in lungs and blocks crucial digestive enzymes produced in the pancreas from reaching the intestines, impairing the ability to break down certain foods. The symptoms of CF can be highly variable. They can be mild in some people and cause a life-threatening illness in others. Symptoms include: •

No bowel movements in first 24 to 48 hours of life

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Stools that are pale or clay colored, foul smelling, or that float

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Infants may have salty-tasting skin

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Recurrent respiratory infections, such as pneumonia or sinusitis

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Coughing or wheezing

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Weight loss, or failure to gain weight normally in childhood

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Diarrhea

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Delayed growth

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Fatigue

The defective gene that is responsible for causing cystic fibrosis is on chromosome 7.

The location of the CFTR gene on chromosome 7

CF is inherited in an autosomal recessive manner so both copies of the defective gene are necessary for a person to develop the disease. If both parents are CF carriers, the child has a 25% chance of inheriting both defective copies and developing CF, and a 50% chance of inheriting one defective copy and being a carrier. According to the Cystic Fibrosis Foundation, about 30,000 Americans, 20,000 Europeans, and 3000 Canadians have CF. In the United States, about 12 million people are carriers, and every year 2500 babies are born with CF. The disease affects all racial and ethnic groups, although it affects

Caucasians with northern European ancestry more often than other populations. It is the most common autosomal recessive genetic disorder in Caucasians, occurring in about 1 in 1600 births. In African Americans, CF affects 1 in 13,000 babies; in Asian Americans, 1 in 50,000 are affected. One in 22 Caucasians are carriers. Genetic testing can identify carriers, but the tests are only 80%-85% accurate because not all of the several hundred mutations that can cause CF are detectable. Due to huge improvements in treatment, the expected life span of people with CF has increased dramatically. Before the mid-1960s, the average age of death of children with CF was 2 years. That meant that one-half of babies born with CF died by the age of two. By the early 1990s, the median age of death had increased to 25 years. It is predicted that babies born with CF since the 1990s can expect to live for 40 years or more. CF patients are usually diagnosed before they are 3 years old. The only way to cure CF would be to use gene therapy to replace the defective gene or to give the patient the normal form of the protein before symptoms cause permanent damage. Because gene therapy is an experimental treatment and requires a great deal more research before it is approved as an option for therapy, the best that doctors can do is treat the symptoms, especially bacterial infections and respiratory discomfort with the goal of maintaining quality of life. Cystic Fibrosis is only one of a multitude of genetic diseases. While there are no cures as of yet for Cystic Fibrosis, researchers are searching for them through various methods, including stem cell research, homeopathy, etc. While screening of the family of a CF patient may reveal the Cystic Fibrosis gene in 60 to 90% of carriers, depending on the type of test used, there are still major breakthroughs to be made in this field.

References: MedlinePlus Medical Encyclopedia Wikipedia, the free Encyclopedia: Cystic Fibrosis Encarta: Cystic Fibrosis LabCorp Cystic Fibrosis – Pulmonology Channel