It assumes that the majority of deleterious mutations are only slightly deleterious, and affect the individual such that the introduction of each additional mutation has an increasingly large effect on the fitness of the organism.
Asume que a maioría das mutacións prexudiciais son só lixeiramente prexudiciais, e afectan ao individuo de maneira que cada mutación adicional ten un efecto cada vez maior sobre a fitness do organismo.