Theoretical study of genetic variability, assuming stepwise production of neutral and very slightly deleterious mutations.

Mathematical treatments are presented that enable us to compute the amount of genetic variability maintained in a finite population, assuming that mutations occur in stepwise fashion and that both selectively neutral and slightly deleterious alleles are involved. Two numerical examples show that, if very slightly deleterious mutations are prevalent, the amount of genetic variability increases much more slowly as the population number increases than is the case when all the mutations are strictly neutral.