DNA contains the instructions, called genes, that control a body's structure and function. When DNA is mutated, instructions become changed or erased. This can lead to disease. Most genes have two copies; if one gets damaged, there is a backup. Therefore, many genetic diseases do not show up unless both copies are damaged. However, some happen when only one copy has gone bad or when there is no backup copy. Some mutations are passed to children from their parents, while others occur spontaneously in the affected individual.
Cystic Fibrosis
Cystic Fibrosis (CF) is one of the most common genetic diseases in the United States. It is caused by a change in a gene called CFTR. A December 2009 report by "Anesthesia & Analgesia" summarizing the genetic basis of CF noted that there are more than 1,000 possible changes in the CFTR gene that can cause CF, and that approximately one of every 29 Caucasian Americans have a mistake in one copy of their CFTR gene. These people do not have CF since they still have one good copy of the CFTR gene. However, when both parents have one damaged CFTR gene, they have a 25-percent chance that any child of theirs will inherit one bad copy of CFTR from each parent and have cystic fibrosis. As of 2010, there is no cure for CF, but a number of therapies have been developed that can treat the symptoms associated with cystic fibrosis. (See Resources.)
Duchenne Muscular Dystrophy
Duchenne muscular dystrophy (DMD) is one of nine diseases that primarily affect voluntary muscle function. The disease is caused by a mistake in the gene that makes a protein called dystrophin. The DNA that is used to make dystrophin protein is located on the X chromosome. Since males only have one X chromosome, they only have one copy of DNA that makes this protein; there is no backup. Females have two X chromosomes and so have two copies of the gene. Because males only have a single copy of the gene, this disease is much more common in males. Affected individuals experience muscle weakness throughout their bodies that eventually leads to paralysis and a life expectancy of fewer than 35 years. "Current Opinion in Neurology" published an article in October 2009 reviewing some of the treatments available for DMD patients. (See Resources.)
Pompe Disease
Pompe disease is caused by a change in the DNA that produces the protein acid alpha-glucosidase (GAA). This protein is essential for breaking down a complex sugar known as glycogen. Loss of this enzyme results in glycogen buildup and cellular damage, especially in muscles. Pompe disease occurs when both copies of the GAA gene have been damaged. According to a September 1999 article in "European Journal of Human Genetics," it is a very rare disease affecting one in 40,000 people worldwide. The only treatment is to replace the protein that is missing. In 2010, the development of a drug for this disease garnered national attention through the release of the film "Extraordinary Measures," which chronicled the heroic efforts of one parent's fight to develop a treatment to save two of his children who have Pompe disease. (See Resources.)
References
- "Anesthesia & Analgesia;" Perioperative Management of the Adult with Cystic Fibrosis; J.L. Huffmyer, K.E. Littlewood, E.C. Nemergut; December 2009
- "Current Opinion in Neurology;" Emerging Genetic Therapies to Treat Duchenne Muscular Dystrophy; S.F. Nelson, R.H. Crosbie, M.C. Miceli, M.J. Spencer; October 2009
- "European Journal of Human Genetics;" Frequency of Glycogen Storage Disease Type II in The Netherlands; M.G.E.M. Ausems, et.al.; September 1999
