The harmful allele of sickle cell anemia has not been eliminated from the human population. Such afflicted people derive some other benefit. Discuss.

(B) The harmful alleles are typically eliminated from a population over time,yet sickle cell anemia persists in the human population. This is because while the homozygous condition $(Hb^S Hb^S)$ is harmful,the heterozygous condition $(Hb^A Hb^S)$ provides a survival advantage against malaria.
The malaria-causing parasite,$Plasmodium$,spends part of its life cycle in red blood cells and triggers an abnormal drop in oxygen levels within the cell.
In carriers $(Hb^A Hb^S)$,this drop in oxygen is sufficient to trigger the sickling of red blood cells. These sickled cells are then rapidly removed from circulation by the spleen,which significantly limits the progression of the malarial infection.
These individuals possess a high resistance to malaria and have a greater chance of surviving outbreaks.
This resistance to infection is the primary reason the $Hb^S$ allele persists in the population. It is found at the highest frequency in regions where malaria is or was a serious health problem.
In contrast,normal individuals $(Hb^A Hb^A)$ are fully susceptible to $Plasmodium$ infection.