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Introduction to the Genetics of Sickle Cell Disease

written by: VinceSummers•edited by: Paul Arnold•updated: 7/15/2009

Sickle cell disease is the most common inherited blood disorder in Americans, and affects millions of people worldwide.

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    Sickle Cell Disease Facts

    The term sickle cell disease refers to a family of inherited blood disorders that usually have an early childhood onset. These disorders are caused by mutations in the gene that codes for a protein called hemoglobin. Hemoglobin is very important, as it allows red blood cells to transport oxygen around the human body.

    People with sickle cell disease make sickle-shaped red blood cells, rather than the normal disc-shaped cells. These sickle cells die at a faster rate than normal cells, and so the abnormality can lead to a low blood count (anemia), and pain episodes caused by the cells blocking blood vessels.

    The body’s tissues need oxygen in order to function and a reduction in red blood cells can lead to damaged organs. The spleen is often affected, which makes a person with a sickle cell disease more vulnerable to infection. Other symptoms include jaundice, and delayed growth and puberty.

    Sickle cell disease is found all over the world, and severity can vary. Treatment for sickle cell disease usually involves treating symptoms and complications, including the use of blood transfusions, antibiotics and painkillers. Sickle cell disease has received a lot of research interest, and so new treatments will probably become available.

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    Inheritance of Sickle Cell Disease

    Sickle cell disease has an autosomal recessive pattern of inheritance. This means that a person with the disorder would have received a mutated version of the gene from each parent. If both parents are carriers (they have one mutated gene and one normal gene each), their children will have;

    • A 25% risk of inheriting sickle cell disease
    • A 25% of having no disorder
    • A 50% chance of being a carrier. Carriers are referred to as having “the sickle cell trait”, and these people are usually healthy.

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    The Gene Involved in Sickle Cell Disease

    The sickle cell gene is HBB (hemoglobin beta) and is located on chromosome 11. The sickle cell gene can mutate in several different ways, meaning there are different types of sickle cell disease.

    According to the What is Sickle Cell Disease? article on the Sickle Cell Disease Association of America website, the most common types are, “Sickle Cell Anemia, Sickle-Hemoglobin C Disease, Sickle Beta-Plus Thalassemia and Sickle Beta-Zero Thalassemia.”

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    Testing for Sickle Cell Disease

    A blood test can determine whether or not a person has sickle cell disease. Prenatal testing is also available, and in some states in America, newborn testing is standard. Those concerned about the genetic disorder and their families sometimes seek genetic counseling.

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    References

    • Sickle Cell Disease, Learn.Genetics: Genetics Science Learning Center website, updated: 12th December 2008, accessed: 13th July 2009, no author specified.
    • Sickle cell disease, Genetics Home Reference website, last updated: 26th June 2009, accessed: 13th July 2009, no author specified.
    • Genetic Disease Profile: Sickle Cell Anemia, US Department of Energy Office of Science website, last updated: 5th May 2009, accessed: 13th July 2009, no author specified.
    • Learning About Sickle Cell Disease, National Human Genome Research Institute website, last updated: 23rd February 2009, accessed: 13th July 2009, no author specified.