Answer:
The mutant allele has stayed around because it protects its carrier from dying of malaria.
Step-by-step explanation:
The sickle-cell allele is extensively recognized as a modified that reasons red blood cells to be distorted into a sickle form when deoxygenated in SS heterozygotes, in which A designates the non-mutant form of the β-globin gene, and also delivers confrontation to malaria in SS heterozygotes. Malaria is related with enlarged severe stage protein attentions and severe malaria rises erythrocyte inflexibility, which may disturb the association among haemoglobin and haematocrit.