In experiments with laboratory populations of Drosophila melanogaster,Mukai and Burdick (1959)observed that a lethal allele maintained a higher than expected frequency.The explanation for this observation is that,at equilibrium,the selective advantage of the lethal allele when it occurs in heterozygotes balances the disadvantage of the allele in homozygotes,and is termed ________.
A) equilibrium distribution
B) underdominance
C) allelic frequency dependence
D) overdominance
E) terminal dominance

Question

Quizplus · Accepted Answer

Overdominance is the phenomenon where a heterozygote has a greater fitness advantage than either of the corresponding homozygotes, leading to the maintenance of genetic variation of the allele. In this case, the lethal allele has a fitness advantage as a heterozygote, balancing the fitness disadvantage as a homozygote, resulting in the higher-than-expected frequency at equilibrium.

In Experiments with Laboratory Populations of Drosophila Melanogaster,Mukai and Burdick