Sickle-cell anemia is a genetic disease prevalent among people of African descent, whereby individuals homozygous for the sickle-cell trait (ss) have red blood cells that readily collapse (and look like a sickle) and are limited in their ability to carry oxygen. While ss individuals can die due to the genetic defect, the evolutionary trade-off is that the ss cells are not readily infected by the malaria parasite, and provide a form of protection for ss carriers (kind of important in Africa where malaria is a significant disease). In contrast, normal homozygous individuals (SS) have red blood cells that carry oxygen normally, but are easily infected with the malaria parasite, and many SS individuals can become very ill from the parasite. Individuals with the heterozygous condition (Ss) have some sickling of red blood cells, but generally not enough to cause mortality. In addition, malaria cannot survive well within these “partially defective” red blood cells. Thus, heterozygous (Ss) individuals tend to survive better than either of the populations with the homozygous conditions (SS or ss). If 9% of an African population is born with a severe form of sickle-cell anemia (ss), what percentage of the population will be more resistant to malaria because they are heterozygous (Ss) for the sickle-cell gene? (5 points)