In this activity (app. 25 min), students are introduced to CRISPRs (clustered regularly interspaced short palindromic repeats) and explore how these are used to edit genomes, not only at the individual level, but, potentially, of at the level of the population. The activity contains a mixture of lecture and questioning, with a culminating activity that clearly demonstrates to students the mechanism by which CRIPSR can be used to effectively alter the genome of a significant proportion of individuals (here, mosquitos) within a population after only a few generations. The activity also highlights the difference between Mendelian inheritance and expected allele frequency changes over time according to Mendelian mechanisms and allele frequency changes anticipated using CRISPR. The activity is designed for Biology 1113 (undergraduate majors course) and can be used without modification for both large and small class sizes. *URL links directly to the folder containing all related resources.