What does the sickle cell allele primarily affect?

The sickle cell allele primarily affects the shape of red blood cells. In individuals with the sickle cell allele, the normal hemoglobin (hemoglobin A) is replaced by an abnormal form known as hemoglobin S. This alteration causes red blood cells to assume a characteristic crescent or "sickle" shape, especially under conditions of low oxygen. These sickle-shaped cells are less flexible and can become stuck in small blood vessels, leading to various complications, including pain and reduced blood flow to organs. This condition is known as sickle cell disease, and it is a direct consequence of the genetic changes introduced by the sickle cell allele.

Other options are related to different aspects of blood and respiratory health but do not directly pertain to the primary impact of the sickle cell allele, which is specifically the structure and functionality of red blood cells.