Allele frequency refers to the fraction of individuals with a particular version of a given gene. what effect does genetic drift have on the allele frequency of a population? a. it causes the allele frequency to resemble that of a small number of individuals that became separated from the rest of the population. b. it causes random changes and the allele frequency of certain traits may increase or decrease. c. it increases the frequency of alleles that improve a species' survival in a particular environment. d. it greatly reduces the total population, which increases the effects of natural selection on allele frequency.