two beta globin chain alleles (the Hb A normal allele and the HB S sickle cell anemia allele) that both circulate at high frequencies in subtropical regions where malaria is a threat

A) directional selection
B) sexual dimorphism
C) sympatric speciation
D) balanced polymorphism
E) coevolution
F) allopatric speciation
G) key innovation
H) adaptive radiation

Question

Carrington Cruickshank · Accepted Answer

Final Answer : D, Explanation :  The prevalence of the Hb A and Hb S alleles in subtropical regions where malaria is prevalent suggests balanced polymorphism, where both alleles are maintained at high frequencies due to their selective advantages in different conditions. The Hb A allele protects against malaria while the Hb S allele provides some protection against severe forms of malaria.

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