Use the following information to answer the questions below.
In those parts of equatorial Africa where the malaria parasite is most common,the sickle-cell allele constitutes 20% of the β hemoglobin alleles in the human gene pool.
-The sickle-cell allele is pleiotropic (i.e.,it affects more than one phenotypic trait).Specifically,this allele affects oxygen delivery to tissues and affects one's susceptibility to malaria.Under conditions of low atmospheric oxygen availability,individuals heterozygous for this allele can experience life-threatening sickle-cell "crises." Such individuals remain less susceptible to malaria.Thus,pleiotropic genes/alleles such as this can help explain why