Problem
The HbS gene and resistance to malaria*
The HbS gene causes sickle cell anemia, a life-threatening, inherited disease that causes red blood cells to collapse and become crescent-shaped instead of round. People with sickle cell disease inherit the HbS gene from both parents. These people have problems with oxygen transport, which causes severe anemia, delayed growth and puberty, complications during pregnancy, among other symptoms.
The high occurrence of this gene coincides with areas in which malaria cases are reported (for example, in tropical areas), an infection caused by a parasite that develops in red blood cells. Individuals who carry the sickle cell gene have an advantage because the parasite cannot develop, making them resistant to malaria and also do not have sickle cell anemia.
Source: Marrero-Delgado, GA (2016).
A. How is the mechanism of natural selection represented in this situation?
B. How does the increase in the occurrence of the HbS gene represent an adaptation?
C. What role do mutations play in this case?