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Genetics behind Sickle Cell Anemia

Page history last edited by qpeters@... 11 years, 4 months ago

Genetics behind Sickle Cell Anemia

 

Sickle cell conditions are inherited from parents the same way blood type, eye color and other physical traits are inherited. The types of hemoglobin genes inherited from parents influences the types of hemoglobin that that said individual makes in their red blood cells. For example a 50% chance of a child having the sickle-cell disease or the sickle-cell trait, or that said child having a 25% chance of having the sickle-cell disease, depends on the status of both parents.

Someone receiving both defective alleles from their parents would develop the disease; however if a said individual inherits a single defective allele, they would have the sickle cell trait and remain healthy, but is known as a carrier.

A 1-in-4 chance and a 1-in-2 chance exist, of a child developing the disease or being a carrier, respectively, that is if both parents are carriers. Sickle cell patients are resistant to malaria, hence carriers produce just enough sickled red cells to serve that purpose; seen that the mentioned gene is incompletely recessive.

Hemoglobin consists of two subunits called alpha-globin and another two named beta-globin. A mutation in the HBB gene produces abnormal versions of beta-globin such as hemoglobin C (HbC), E (HbE) and S (HbS). The beta-globin was ultimately made from instructions by the HBB gene. An abnormality known as thalassemia may also result from a HBB mutation resulting in low levels of beta-globin.

Sickle cell anemia is caused by a mutation in the HBB gene. This as mentioned before is a common form of the sickle cell disease. With this condition both beta-globin subunits in hemoglobin is replaced by hemoglobin S. In other forms of the disease, only one beta-globin is replaced; a different hemoglobin replaces the other.

The premature death of the sickle-shaped red blood cells leads to sickle cell anemia. This results from the dissolution of red blood cells into a sickle shape caused by abnormal versions of beta-globin. Sickle-cell anemia is due to an autosomal recessive allele which is found on the short arm of chromosome 11.

 

 

 

 

Image showing the defective red blood cells and its migration through blood vessels 

 

 

 

Diagram showing the transfer of defective alleles from parents to offsprings 

 

 

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