Sickle Cell Anemia

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to the vessels of the heart but cause a blockage there also. This is called thrombosis (Parker, Parker).
The disorder is caused by a single change in the amino acid building blocks of the oxygen-transport protein, hemoglobin. This protein, which is the component that makes red cells “red”, has two subunits. The alpha subunit is normal in people with sickle cell anemia. The beta subunit has the amino acid valine at position 6 instead of the glutamic acid that is there normally. This alteration is the basis of all problems that occur in people with sickle cell anemia. The molecule, DNA (deoxyribonucleic acid), is the fundamental genetic material that determines the arrangement of the amino acid building blocks in all proteins. Segments of DNA that code for particular proteins are called genes. The gene that controls the production of the B-subunit of hemoglobin is located on one of the 46 human chromosomes (chromosome #11). People have 22 identical chromosome pairs (the 23 pair is the unlike X and Y-chromosome that determine a person’s sex). One of each pair is inherited from the father, and one from the mother. Occasionally, a gene is altered in the exchange between parent and offspring. This event, called mutation, occurs extremely infrequently (Campbell, Reece).
Therefore, the inheritance of sickle cell anemia depends totally on the genes of the parents. If only one of the B-globin genes is the “sickle” gene and the other is normal, the person is a carrier. The condition is called sickle cell trait. With a few rare exceptions, people with sickle cell trait are completely normal. If both B-globin genes code for the sickle protein, the person has sickle cell anemia. Sickle cell anemia is determined at conception, when a person acquires his/her genes from the parents. You may find the following diagrams useful to help you understand how sickle hemoglobin is inherited. In all the following diagrams you wi...