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Examples of Common Genetic Disorders

written by: Jennifer Gonzalez •edited by: Leigh A. Zaykoski•updated: 6/30/2011

Genetic disorders are disorders concerning the DNA that is passed on from parents to their children. While this can be a frightening thing to think about, it is important to learn about the most common examples of genetic disordersso you can find out about treatment and preventive measures.

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    What is a Genetic Disorder?

    dna A genetic disorder is a type of disease that occurs when there is some kind of change in the natural makeup of a person’s DNA. This happens when there are different mutations, or damage, in a person’s genes or chromosome lineup. A person generally develops a genetic disorder because the parents have passed it on, or there has been a history of a genetic disorder in the family.

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    Common Genetic Disorders

    Examples of genetic disorders:

    • Down Syndrome: Down syndrome occurs when there is an extra copy of a certain chromosome present. Another cause for Down syndrome, although less likely, is a disease called Robertsonian translocation. This happens when two chromosomes break apart and then rejoin once again; this creates one cell with two chromosomes. One in every 800 births results in a baby with Down syndrome. Although many Down syndrome pregnancies end in the mother having a miscarriage, the babies that do make it to term have a great chance for success. This of course depends on other aspects of the disease, such as heart defects. Many Down syndrome patients appear to have a flattened face, with eyes that are slanted in an upward direction. A short neck and a tongue that is protruding are also symptoms in people with Down syndrome.
    • Cystic Fibrosis: Cystic fibrosis occurs when there is a mutation in the gene for the protein cystic fibrosis transmembrane conductance regulator. Many people have two copies of this gene, and in order to prevent this disease, a person would only need one of those genes to function properly. Cystic fibrosis happens when neither of those two genes is properly functioning. This gene is important for the proper control of sweat, mucus and digestion. This type of genetic disorder affects the person's entire body, causing disability, and in some occasions, an early death. With cystic fibrosis, the most common symptom is difficulty breathing, most likely caused by repetitive infections in the lungs. Poor growth, sinus infections and diarrhea are all symptoms of cystic fibrosis. In some cases, infertility can occur.
    • Sickle-Cell Disease: This disease occurs when there is a mutation in the hemoglobin-Beta gene that is found on chromosome 11. In sickle cell disease, hemoglobin S (abnormal hemoglobin molecules) causes the blood to stick together and form a rod-like shape. This causes red blood cells to become stiff and take on the shape of a sickle, which then causes the blood cells to mend together and form a blockage to vital organs. This disease is the most commonly inherited blood disorder in the United States. Common side effects are anemia, restricted blood flow to organs, pain, stroke, a painful and long-lasting erection and bacterial infections. Damage to the spleen, kidneys, and liver has also been reported.
    • Hemophilia: Hemophilia is an X chromosome genetic disorder that makes the body unable to control blood clotting. This is necessary to stop the blood flow in a broken blood vessel and other wounds by forming a protective scab. A person with this disorder does not bleed more than normal, but they may bleed for longer periods of time than someone without this disorder, and in some cases they may never heal completely. Symptoms of this disorder consist of bouts of internal and external bleeding, along with frequent bruising.
    • Edward Syndrome: This is caused when a person has an extra chromosome 18 in every cell. 80 percent of people with this condition are female, and only 5 to 10 percent of people born with this illness will live to the age of one. This illness is the second most common autosomal trisomy, next to Down syndrome, and the rate for a baby developing this disease increases as the age of the pregnant mother increases. Physical symptoms of this disorder include a small head, small mouth and clenching fists. Other symptoms are mental retardation, delays in development, heart defects, undeveloped lungs, kidney malformations and breathing difficulties, just to name a few.
    • Patau Syndrome: Patau syndrome is caused when there are three copies of chromosome 13 in each cell. 95 percent of babies born with this syndrome will pass away before their first birthdays, and out of that 95 percent, the expected life span is up to seven days. This disorder causes severe mental retardation along with numerous medical problems. Other symptoms are a cleft lip or cleft palate, eyes that are small and closely set, extra fingers, having only one hemisphere of the brain, low muscle tone and an abnormal skeleton.
    • Chronic Myelogenous Leukemia: This essentially occurs when a piece of chromosome 22 and chromosome 9 break off and switch places with one another. This is cancer of the bone marrow that is caused by the rapid growth of blood cells. Chronic myelogenous leukemia is responsible for up to 20 percent of all leukemia cases. Symptoms include fever, a feeling of weakness, feeling tired, bleeding, easy bruising and a swollen spleen. An increased amount of white blood cells with a decreased amount of red blood cells and platelets is a telltale sign of this illness. A person may not be born with this illness; however, it can develop over time without warning.
    • Triple X Syndrome: This occurs when a female is born with three copies of the X chromosome in each cell. One in 1,000 newborn girls are born with this syndrome every day. Women with this syndrome may be unable to reproduce, have irregular periods and have a mild learning disability. Other than that, no physical differences have been reported.

    • Neurofibromatosis- Neurofibromatosis is caused by a mutation of the chromosome 17q11.2. This disorder causes the nerve tissue to grow tumors over the body. Some may be benign, while others can cause nerve and tissue damage. One copy of the effected gene is needed for this disorder to take place, so if one parent has this disorder, their child will have a 50 percent chance of developing it as well. Learning disabilities, epilepsy, and multiple surgeries are all associated with this disorder.

    • Angelman Syndrome- Angelman syndrome is caused by the inactivation of chromosome 15 on the maternal side, while the paternal copy is overridden. This syndrome primarily affects the nervous system. Hyperactivity and a short attention span are noted with this disorder, along with sleeping disorders, developmental delays, impaired speech, trouble keeping balance, seizers, a small head, jerky movements, and frequent laughing or smiling.

    Today, genetic testing can be performed on an unborn fetus that will allow the parents to learn if their child is at risk of developing a genetic disorder. While genetic disorders can seem to be frightening, many people with these disorders live a long, happy, and fulfilled life.

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    References

    Examples of Genetic Disorders; http://www.hudsonalpha.org/education/kits/disorder-detectives/genetic-disorders

    Specific Genetic Disorders; http://www.genome.gov/10001204

    What are Genetic Disorders; http://www.genome.gov/19016930

    Image: DNA Molecule by net_efekt Under CC BY 2.0