Bridget Dawkins was complaining of hip pain. Weeks later she would have a fever, and chest pain. While playing basketball with her neighbors she collapsed. The doctors at the local hospital told Bridget's mother, Shawna, that their daughter was diagnosed with sickle cell anemia. Surprisingly the doctor made a comment that people of African descent have the highest chances of having sickle cell anemia. Shawna wondered; "what exactly is sickle cell anemia? How is it caused? Why do African Americans have the highest chance of having sickle cell anemia only?" The point of the matter is that sickle cell anemia is most dominant in the African American race than any other race.
The name sickle cell anemia is not far from the shape a cell takes when a person has this disease. The disease itself is an inherited blood disorder which deals with hemoglobin. In our bodies every red blood cell contains around 200-300 hemoglobin molecules.
Micrograph of a piece of karan bagga's, student fr...
based on http://www.understandingrace.org/humvar/s...
English: Description Malaria versus sickle-cell tr...Hemoglobin serves as the most important and complex component of a red blood cell. Its role is to bind oxygen in exchange for carbon dioxide in the lungs. The red blood cells that are now oxygenated release oxygen in the exchange for carbon dioxide to the body's tissue. An important use of oxygen lies in the mitochondria which is the power house of the cell. Red blood cells are responsible for carrying oxygen in order to nourish tissues and sustain life. There shape is small and have flexible inner tubes. This shape serves many advantages. Among them are a large surface area that absorbs oxygen and carbon dioxide. The flexibility makes it easy to move through capillaries and tiny blood vessels which join the arteries and veins. "Sickle cell disease occurs in genetic abnormalities in hemoglobin." (Gillie January 2004: 12)
Hemoglobin A is a normal molecule in the red blood cells when a person has sickle cell anemia they get a different hemoglobin. This molecule is called Hemoglobin S. The difference between these two molecules is in a protein that has an amino acid chain. In a normal hemoglobin there are 2 alpha and 2 beta chains. When a person has hemoglobin S the 4 chain tetramer has a substitute glutamic acid in both the beta chains. A slight difference can cause trauma. "The destructive nature of the sickle hemoglobin develops when it loses oxygen." (Harris March 2001:17) When the molecule becomes deoxygenated it forms polymers which are best described as rigid rods. These polymers distort the red blood cells and gives them the sickle shape. This change called polymerization is the leading change to sickle cell anemia. The polymers don't form as one strand but as "strand that forms together." In appearance they seem to have a strong bond but in reality they a have a weak interaction. Hemoglobin becomes polymerized when it release oxygen. These cause the membranes in the cell to distort which damages the cell.
Genetically if we are looking at this disease we known that in our bodies' chromosomes are found in the genes. "DNA (deoxyribonucleic acid) is the fundamental genetic material that determines the arrangement of the amino acid building blocks in protein." (Harris March 2001 35) We know that segments of DNA are genes that are specified for certain proteins. When a person has sickle cell anemia the gene controller of beta globins are found on chromosome #1. Humans have 46 chromosomes. Twenty two of these chromosomes are identical but the twenty third pair is the chromosome that determines a person's sex. We inherit one of each pair from our mothers and fathers. Sometimes the gene can be altered between parents and their children. This is called mutation. This is how sickle cell anemia can be inherited from parents. If one of the beta genes is sickled when given to an offspring but the other one is normal then the person has sickle cell trait. These people are then heterozygote. If the offspring receives both of the beta globin genes sickled then they have sickle cell anemia. Basically of the parents both have the trait of the disease and they both pass on the genes their child will have the disease. Science has proven that balancing selection has to do with who acquires it and why. "This situation where selection actively maintains two or more alleles at a locus, is called balancing selection." (Sigler December 1981:22)
Locus is the position that a specific gene occupies on a chromosome. An allele is a member of series of genes that occupy a specific chromosome. Heterozygotes can cause balancing selection to arise. Heterozygotes have a selective advantage due to the sickle trait. In many cases one species can have alleles that are similar to other species than their own. This occurs at the histocompatibility meaning that his is a condition in which the absence of immunological interference permits the grafting of tissue or the transfusion of blood without rejection. The body will accept the blood. Having two different alleles like the sickle cell trait provides its advantages.
An advantage to having the trait would be a resistance to malaria. Malaria has a huge existence in Africa. This would mean that many Africans have a resistance to malaria but prevalence to sickle cell anemia. The reasons African Americans have a higher rate is because of balancing selection. Darwin says that over time humans have evolved and learn to adapt to their environment. Malaria has been around Africa for years. The genes in our bodies created a resistance to malaria but in return got prevalence to sickle cell anemia.
This disease has severe impacts with determining factors. Polymerization can cause the loss of oxygen. This can lead to damage to the organs. The lungs are hugely impacted because they supply the oxygen to unsickle the cell. This leads to dangerous acute episodes of chest pain. "Factors that make sickle cell anemia worse would be the acidity of the environment." (Sacerdote 2001: 19). The lower the acidity the better because the organ's that suffer the most damage is the spleen and bone marrow. Some patients are born with hemoglobin F but this hemoglobin doesn't polymerization. The red blood cells continue to function normally. Hemoglobin tends to lose oxygen after strenuous exercise. Another symptom would be lodging of heme in the red cell membrane. The iron promotes dangerous compounds. These are called oxygen species. The membrane becomes stiff and both lipid and protein in the molecule damages. The shape of sickle cell damages the small capillaries and vessels because of the unusual shape.
Although this disease is very harmful and devastating there are ways to make these episodes less painful. They have come up with a treatment for sickle cell anemia. Three hundred patients with severe sickle cell anemia participated in the "Multicenter study of Hydroxyurea in sickle cell anemia." (Sean Henahan accessed October 3, 2005). In this study they developed a therapy which showed reductions in the frequency of chest pain, fever and abnormal chest x-rays. "Although it is not a cure, hydroxyurea therapy is the first effective treatment for this serious illness and may greatly improve the quality of life of sickle cell anemia patients." (Dr. Claude Lenfant, Director, National Heart, Lung and Blood institute.) The only problem is that scientists are unsure why the drug works.
According to recent statistics approximately 72,000 Americans are affected with this disorder. The disorder is present in one in every 500 African Americans. It is estimated that two million African Americans have the sickle cell trait. This means that one in every twelve African Americans carry the trait. African Americans not only have the highest chance of having the sickle cell disease and trait but it also serves to them as an advantage. The disease itself is very painful and there is no cure. (Sacerdote November 2001:25) Although the disease itself can occur in any race and anyone it seems to have its favorites amongst the African American race. Luckily the disorder can be detected early enough in order for help to be instituted. Research is still being done in order to find the cure but the remnants of the disease will forever be put down in history.