A team of researchers led by Leonid Kruglyak have developed a technique using the gene editing system CRISPR to rapidly identify gene variants. The findings could significantly improve efforts to map out genes and determine their function. Traditionally, work to identify gene variants has been limited to results from studies done at the low resolution of the rate of naturally occurring meiotic recombination, which is when a cell divides twice to produce germ (reproductive) cells and genetic material is "shuffled." Often, these recombination rates are too low to resolve mapped regions to individual genes, much less to specific variants within genes. Mitotic recombination, which affects somatic cells, can provide a more detailed understanding of gene function and variants because it sometimes leads to the formation of a recombined chromosome with only one set of genes, rather than two sets. This causes the genes to lose their function, which provides important insights into what critical role they play. Yet, mitotic recombination is a rare event. Here, Kruglyak and colleagues used CRISPR to induce mitotic recombination, allowing for detailed mapping of trait variants. They demonstrate this technique by identifying a genetic mutation that makes yeast sensitive to manganese.