 The simplest model for analysing migration assumes that a given population receives a number of migrants each generation, but sends out no emigrants. Suppose the frequency of the \(A_1\) allele in the resident population is \(p\), and the frequency of the \(A_1\) allele among the migrants arriving in the population is \(p_m\). The proportion of migrants coming into the population each generation is \(m\) (i.e., as a proportion of the resident population.) So post-migration, the frequency of the \(A_1\) allele in the population is: