Question

What is heterozygote superiority? In a two-allele system, how does heterozygote superiority affect allele frequencies? What are the evolutionary implications of this for recessive lethal alleles? Use Mukai and Burdick’s experiment to illustrate the above. (based off of ch6 and 7 of evolutionary analysis 5th edition)

Answer 1

Heterozygote superiority is a phenomenon where there is a higher relative fitness of the heterozygote genotype than the homozygote dominant as well as recessive. This is also called heterozygote advantage as in case of Sickle cell anemia. In a two-allele system, heterozygote superiority affect allele frequencies by maintain the diversity i.e. heterozygosity in a population i.e. it maintains the variability in the genotype. The evolutionary implications of this for recessive lethal alleles in case of Heterozygote superiority is that the allele will be kept in the gene pool and not eliminated. For e.g. Sickle cell anemia deleterious in homozygous condition; but in heterozygous condition in a place where malaria is common, the allele confers resistance to malaria and is maintained.