Answer:
Sickle cell anaemia is a generic disorder which affects the red blood cells. The red blood cells assumes a sickle shape and contains lesser amount of the protein hemoglobin. Hemoglobin helps in the necessary transport of oxygen to other parts of the body.
The sickle cell allele is known to be advantageous to mainly people who stay in developing/underdeveloped counties who malaria endemic . People with the sickle cell allele have a higher chance of survival against malaria than people without this allele.
In modern countries malaria isn’t prevalent there due to the lack of vectors, poverty and environmental conditions which tends to support the survival of the mosquito. This means the sickle cell allele isn’t advantageous in this region.