Substitution processes in molecular evolution. III. Deleterious alleles

A study of the substitution processes for different models of harmful alleles through mathematical analyses and computer simulations reveals that the rate of substitution has a concave relation to the selection strength. The models studied include the house-of-cards model, the Hartl-Dykhuizen-Dean (HDD) model, the exponential and gamma shift models and the optimum model. While the HDD and optimum models represent silent evolution adequately, no model represents protein evolution satisfactorily due to the variability in substitutions exhibited by them.