Their allele frequencies at numerous genetic loci gradually become more and more different as new alleles independently arise by mutation in each population.
随着新等位基因在每个群体中独立突变产生，它们在许多遗传位点上的等位基因频率逐渐变得越来越不同。
2
So even though a drug might work well for patients whose tumors have a particular mutation, when the drug is used for a broader population, it shows only a small effect.
所以，即使一种药物对有同一变异的肿瘤患者有效，但当应用于更广泛的患者时就可能收效甚微。
3
The accepted scenario was a simple case of evolutionary selection. In a bacterial population exposed to a killer drug, a few lucky individuals might have a genetic mutation that kept them alive.