10 Easy points!! Propose a reason the frequency of the sickle cell allele remains high in some areas.....?

Well this is caused by the heterozygous advantage. I believe sickle cell is a zygous recessive condition. That means that a heterozygous individual could be a carrier of the lethal allele. This means that if that person has a child with another heterozygous individual, that child may have sickle cell. so you see, that allele is actually "hidden" because the symptoms are not seen, and it will always be there.