Question

In an insect species, survival in agricultural fields regularly sprayed with insecticide is determined by the genotype for a detoxification enzyme encoded by a gene with two alleles, A and D. Which of the following statements is consistent with the data?

1. This will likely lead to the frequency of the A allele being eliminated (f=0.0) and the D allele being fixed (f=1.0).
2. Eventually, natural selection should lead to a balanced polymorphism.
3. The D allele frequency will change faster as it gets less frequent.
4. Both the A and D alleles should reach stable equilibrium frequencies that are maintained in a steady state.
5. Directional selection will increase the frequency of the A allele at a pace determined by the intensity of natural selection.

Genotype	Relative Fitness
AA	1.00
AD	0.70
DD	0.05

Answer 1

Answer: According to the natural selection theory, the allele with better fitness are preferred and passed on to next generations.

Allele fitness frequency of A= 1+ 0.7/2= 1.35

Allele fitness frequency of D= 0.05 +0.7/2= 0.4

Since the allele fitness frequency of D is much less than that of allele A, over the generations, D will get eliminated and A allele will increase at a frequency determined by the intensity of natural selection.

Hence, E. Directional selection will increase the frequency of the A allele at a pace determined by the intensity of natural selection