We just went over this is my bio class. If you have 2 dominant healthy (non-sickle cell) traits, as in the first case, you are sickle cell free but at risk of malaria. On the contrary, if you have 2 recessive sickle-cell traits, you will have sickle-cell. The heterozygous situation is the trickiest to understand so I’ll go over it pretty slowly. Single the healthy allele is dominant, if you have one dominant and one recessive, you are a carrier and will have somewhat healthy cells. Your red blood cells will be fragile and pop relatively easily. How malaria works is it takes host of your red blood cells. However, with these fragile red blood cells, if malaria tries to take host, they pop. Therefore, you are immune to malaria because it cannot take goat of your cells, and you are also free of sickle-cell disease because it is a recessive trait. Comment if you would like me to explain this any further (:
