Kaplan Nursing Entrance Exam Practice 2026 – Comprehensive Prep

The allele frequency for smallpox susceptibility remained constant in the gene pool after the elimination of smallpox due to several factors. While smallpox was a significant selective pressure on the human population, its eradication means that the direct environmental pressure it exerted on individuals with varying susceptibility is no longer present. Therefore, individuals who possess alleles making them susceptible to smallpox continue to exist in the population without facing the mortality risk that would typically diminish their frequency.

Genetic variation in populations can persist even after the selective pressures have been removed, and new alleles can enter or remain in the gene pool through random mating and inheritance. Thus, while the disease is no longer present, the alleles linked to susceptibility do not suddenly disappear or drastically change in frequency without a new reproductive influence or selective pressure. This results in a stable allele frequency among the population over time.