The most prevalent genetic disorder in the USA today is Sickle Cell Anemia (SCA) and affects the red blood cells, also known as erythrocytes or rbcs. Healthy rbcs are concave in the middle. This is because fetal cells lose their nuclei upon birth. This ennucleation causes the cell to sink in on itself. In SCA, the crescent-shaped erythrocytes are rapidly destroyed. This forces a rapid production of new ones. These cells are forced out before they are mature, causing them to retain their nuclei. Couples who believe they may carry the genes for the disease should consult a genetic counselor about sickle cell anemia prevention.
In order for someone to develop the disease, both parents must carry the recessive trait for a specific type of hemoglobin. This trait is called AS. In this case, there is one chance in four that their offspring will inherit the disease. There is also half a chance that they will carry the AS trait and one chance in four that they will neither carry the trait nor have the disease. If one parent has normal hemoglobin, Type AA, and the other has AS, there is half a chance that each child will have the trait but not the disease.
While it is true that African Americans are more commonly affected by the disease than people of other nationalities, it does affect people of Latin American, Italian, Arabic, Greek and Asiatic Indian descent. In fact, people of Hispanic origin are half as likely to get SCD as someone of African American origin. Approximately 1 in 10 African American newborns have the trait and one in roughly 450 develop SCD.
We already know that the SA gene is recessive. If this is the case, why is it such a prevalent disease? The reason for this is that the AS trait confers greater survival with respect to malaria, a deadly condition caused by a parasite carried by mosquitoes and affecting half the world's population. Up until very recently, the reason for this was completely unknown.
In 2011, a paper was published in the prestigious scientific journal, Cell, that shed light on the molecular mechanisms underlying this curious situation. While this is great news for that half of the world for which malaria is a menace, it does little to comfort those who suffer from SCA.
A lot of the signs and symptoms of SCA are the same as for any other form of hemoglobin deficiency. These are shortness of breath, dizziness, headaches, fatigue, coldness in the extremities, paler than normal skin and jaundice (evidenced by a yellow tinge in the whites of the eyes). SCA is also characterized by outbreaks of excruciating pain all over the body.
An SCA crisis occurs when the errant erythrocytes stick together and cut off blood flow, causing damage to major organs (lungs, liver and kidneys). This is also what causes the bouts of unbearable pain. A crisis may go on for hours and then resolve spontaneously or it may persist for days, up to a week or longer.
Currently in the United States, all newborn babies are routinely tested for the AS trait and for SCD. This paves the way for early treatment of the condition. So far, the only of preventing SCD is by having a frank discussion with a genetic counselor and making sometimes difficult decisions regarding family planning.
In order for someone to develop the disease, both parents must carry the recessive trait for a specific type of hemoglobin. This trait is called AS. In this case, there is one chance in four that their offspring will inherit the disease. There is also half a chance that they will carry the AS trait and one chance in four that they will neither carry the trait nor have the disease. If one parent has normal hemoglobin, Type AA, and the other has AS, there is half a chance that each child will have the trait but not the disease.
While it is true that African Americans are more commonly affected by the disease than people of other nationalities, it does affect people of Latin American, Italian, Arabic, Greek and Asiatic Indian descent. In fact, people of Hispanic origin are half as likely to get SCD as someone of African American origin. Approximately 1 in 10 African American newborns have the trait and one in roughly 450 develop SCD.
We already know that the SA gene is recessive. If this is the case, why is it such a prevalent disease? The reason for this is that the AS trait confers greater survival with respect to malaria, a deadly condition caused by a parasite carried by mosquitoes and affecting half the world's population. Up until very recently, the reason for this was completely unknown.
In 2011, a paper was published in the prestigious scientific journal, Cell, that shed light on the molecular mechanisms underlying this curious situation. While this is great news for that half of the world for which malaria is a menace, it does little to comfort those who suffer from SCA.
A lot of the signs and symptoms of SCA are the same as for any other form of hemoglobin deficiency. These are shortness of breath, dizziness, headaches, fatigue, coldness in the extremities, paler than normal skin and jaundice (evidenced by a yellow tinge in the whites of the eyes). SCA is also characterized by outbreaks of excruciating pain all over the body.
An SCA crisis occurs when the errant erythrocytes stick together and cut off blood flow, causing damage to major organs (lungs, liver and kidneys). This is also what causes the bouts of unbearable pain. A crisis may go on for hours and then resolve spontaneously or it may persist for days, up to a week or longer.
Currently in the United States, all newborn babies are routinely tested for the AS trait and for SCD. This paves the way for early treatment of the condition. So far, the only of preventing SCD is by having a frank discussion with a genetic counselor and making sometimes difficult decisions regarding family planning.
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