Genetic Causes of Sickle Cell Anemia
The trait that causes sickle cell anemia is recessive, which means that the disorder will only occur in a person who is homozygous recessive for the sickle cell trait. One way for this to occur is for a person to be an offspring of two parents who are heterozygous for the sickle cell trait. These parents would not have sickle cell anemia because the dominant allele would overshadow the recessive one. However, they would still have the ability to pass on the recessive allele to their children. As shown in the diagram, there is a 25% chance that two parents who are heterozygous for sickle cell anemia would produce a homozygous recessive offspring. There is also a 50% that their child would be a heterozygous "carrier," or someone who has the trait but does not have sickle cell anemia.
Who does sickle cell anemia most commonly effect?
Sickle cell anemia is generally found in people of African descent. In fact, 1 in 12 African Americans carry the sickle cell trait. The genetic disorder is also found in people whose families come from South or Central America (especially Panama), the Caribbean Islands, Mediterranean countries (like Turkey, Greece, Italy), India, and Saudi Arabia.
Survival of Sickle Cell Anemia
People with sickle cell anemia cannot contract Malaria. This quality meant that Africans with the sickle cell trait were able to live slightly longer than those who contracted Malaria, allowing them to reproduce and pass on the sickle cell trait. This process plays a part in the disease's prevalence in many people of African descent.