Have you ever wondered why harmful genetic mutations remain in the gene pool? A mutation in the beta-globin gene provides an example of how a genetic mutation can both help you and hurt you.
With one copy of the mutated gene: individuals are protected against malaria, which is a selective advantage (and so this mutation is sure to stay in the gene pool).
With two copies of the mutated gene, one copy inherited from each parent: individuals develop the harmful genetic disorder called Sickle Cell Anemia.
Sickle cell anemia predominantly affects African Americans because of their recent ancestry in malaria-stricken areas, where it was beneficial to carry one copy of the mutated gene. The disease affects about 1 in 250 - 600 African Americans, but can be found in people of any ethnic background including people of Mediterranean, Middle Eastern, Indian, Central and South American ancestry.
Sickle cell anemia is an inherited chronic disorder in which the body makes abnormally shaped red-blood cells. A normal individual has red blood cells that look like a donut without the hole. But a person with Sickle Cell Anemia is born with red-blood cells that look like a “sickle” or a crescent, which do not move easily through blood vessels. The misshapen red-blood cells tend to stick to the vessel walls, causing these types of symptoms:
pain episodes (arms, legs, chest and abdomen)
a tendency toward infection
pulmonary hypertension (high blood pressure in the arteries that supply the lungs), which often leads to heart failure
anemia (low blood count)
Currently over 2.5 million people in the US carry one copy of the mutated beta-globin gene (and are unaffected carriers of the disease) and more than 70,000 people have Sickle Cell Anemia.
People with Sickle Cell anemia can undergo blood transfusion treatment and take antibiotics to help minimize complications associated with the disease. But these blood transfusions must be continued throughout a person’s lifetime in order to minimize medical problems arising as a result of the disease.
New areas of research for Sickle Cell treatment include the use of Stem Cells — a hot-topic these days — after the breakthrough development that makes it possible to generate new lines of human embryonic stem cells without destroying the embryo.
Missouri pediatrician Dr. F. Sessions Cole, Director of Newborn Medicine at St. Louis Children’s Hospital, said [August 28, 2006]: “Stem cell research has the potential to lead to new treatments and cures for diseases and injuries that affect children of all ages [including] sickle cell disease…”